#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
// #pragma GCC optimize ("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native") // codeforces
// #pragma GCC target("avx,avx2,fma")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,tune=native") // yandex

#include "bits/stdc++.h"
using namespace std;
#ifndef LOCAL
#define endl '\n'
#endif

#define fr(i, a, b) for(int i = a; i <= b; i++)
#define rf(i, a, b) for(int i = a; i >= b; i--)
#define pf push_front
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
#define lb lower_bound
#define ub upper_bound

typedef long long ll;
typedef long double f80;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

int pct(int x) { return __builtin_popcount(x); }
int pct(ll x) { return __builtin_popcountll(x); }
int bt(int x) { return 31 - __builtin_clz(x); } // floor(log2(x))
int bt(ll x) { return 63 - __builtin_clzll(x); } // floor(log2(x))
int cdiv(int a, int b) { return a / b + !(a < 0 || a % b == 0); }
ll cdiv(ll a, ll b) { return a / b + !(a < 0 || a % b == 0); }
int nxt_C(int x) { int c = x & -x, r = x + c; return (((r ^ x) >> 2) / c) | r; }
ll nxt_C(ll x) { ll c = x & -x, r = x + c; return (((r ^ x) >> 2) / c) | r; }

vector<int> get_bits(int mask) {
	vector<int> bb;
	while(mask) { int b = bt(mask); bb.pb(b); mask ^= (1 << b); }
	reverse(all(bb));
	return bb;
}

int get_mask(vector<int> v) {
	int mask = 0;
	for(int x : v) { mask ^= (1 << x); }
	return mask;
}

template<typename T>
void uniq(vector<T> &v) { sort(all(v)); v.resize(unique(all(v)) - v.begin()); }

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

ll rand(ll l, ll r){
	uniform_int_distribution<ll> uid(l, r);
	return uid(rng);
}

void sc() {}

template <typename Head, typename... Tail>
void sc(Head &H, Tail &... T) { cin >> H; sc(T...); }

#ifdef LOCAL
#define debug(...) cerr << "[L:" << __LINE__ << "][" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif

// #ifndef LOCAL
// string to_string(__int128 x) {
// 	string s = "";
// 	bool neg = 0;
// 	if(x < 0) { s += "-"; neg = 1; x = -x; }
// 	if(!x) s += '0';
// 	while(x) {
// 		int rem = x % 10;
// 		s += to_string(rem);
// 		x /= 10;
// 	}
// 	reverse(s.begin() + neg, s.end());
// 	return s;
// }
// #endif

const int mod = 1e9 + 7; // 998244353;

int pwr(int a,ll b) {
	int ans = 1;
	while(b) {
		if(b & 1) ans = (ans * 1LL * a) % mod;
		a = (a * 1LL * a) % mod;
		b >>= 1;
	}
	return ans;
}

/*
	Lookout for overflows!!
	Check array sizes!!
	Clear before test cases!!
	Use the correct modulo!!
	Check for corner cases!!
	Are you forgetting something?!
	Read problem statement carefully!!!
*/

const int N = 1e6 + 5;
const int LOGN = 20;
vector<int> g[N];
bool centroid[N];

int depth[N], par[N], sz[N];
int dist_par[N][LOGN], dsz[N];
vector<pii> dis_child[N];
bool tmp[N];
pii qq[N];

void dfs2(int u,int p){
    tmp[u] = 0;
    sz[u] = 1;
    for(int v : g[u])
        if(v != p && !centroid[v]){
            dfs2(v, u);
            sz[u] += sz[v];
        }
}

int get(int u,int p,int S){
    for(int v : g[u])
        if(v != p && !centroid[v] && sz[v] > S / 2)
            return get(v, u, S);
    return u;
}

int solve(int u){
    dfs2(u, 0);
    int c = get(u, 0, sz[u]);
    centroid[c] = 1;
    int l = 0, r = 0;
    qq[r++] = {0, c};
    tmp[c] = 1;
    pii x;
    while(l < r) {
        x = qq[l++];
        dis_child[c].eb(x);
        dist_par[x.se][dsz[x.se]++] = x.fi;
        int u = x.se;
        for(int v : g[u]) {
            if(!tmp[v] && !centroid[v]) {
                tmp[v] = 1;
                qq[r++] = {x.fi + 1, v};
            }
        }
    }
    for(int v : g[c])
        if(!centroid[v]) {
            par[solve(v)] = c;
        }
    return c;
}
void dfs1(int u,int p) {
    depth[u] = depth[p] + 1;
    for(int v : g[u])
        if(v != p)
            dfs1(v, u);
}

ll c[N];
bool vis[N];
set<pair<ll,int>> q;

void solve() {
    int n, m, a, b;
    sc(n, m, a, b);
    q.clear();
    fr(i, 1, n) {
        dis_child[i].clear();
        dsz[i] = 0;
        g[i].clear();
        centroid[i] = 0;
        vis[i] = 0;
        par[i] = 0;
    }
    fr(i, 1, n) {
        int p;
        sc(p, c[i]);
        // p = i - 1, c[i] = 1;
        if(!c[i]) c[i] = 1e18;
        if(p) {
            g[p].eb(i);
            g[i].eb(p);
        }
    }
    c[a] = c[b] = 0;
    solve(1);
    fr(i, 1, n) {
        reverse(dist_par[i], dist_par[i] + dsz[i]);
        reverse(all(dis_child[i]));
    }
    q.emplace(0, a);
    vis[a] = 1;
    ll ans = -1;
    while(!q.empty()) {
        auto x = *q.begin();
        q.erase(q.begin());
        int u = x.se;
        ll val = x.fi;
        if(val >= 1e18) break;
        if(u == b) { ans = val; break; }
        int p = u, k = 0;
        while(p) {
            int d = dist_par[u][k];
            while(!dis_child[p].empty() && dis_child[p].back().fi <= m - d) {
                int v = dis_child[p].back().se;
                dis_child[p].pop_back();
                if(!vis[v]) {
                    vis[v] = 1;
                    q.emplace(c[v] + val, v);
                }
            }
            p = par[p], k++;
        }
    }
    cout << ans << endl;
}

int main() {
	ios :: sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int t = 1;
	cin >> t;
	for(int tt = 1; tt <= t; tt++) {
        cout << "Case #" << tt << ": ";
		solve();
	}
	return 0;
}