// ~~ icebear ~~
// tag: Dilworth's Theorem
#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef pair<int, int> ii;
typedef pair<ii, int> iii;
 
template<class T>
    bool minimize(T &a, const T &b) {
        if (a > b) return a = b, true;
        return false;
    }
 
template<class T>
    bool maximize(T &a, const T &b) {
        if (a < b) return a = b, true;
        return false;
    }
 
#define FOR(i,a,b) for(int i=(a); i<=(b); ++i)
#define FORR(i,a,b) for(int i=(a); i>=(b); --i)
#define REP(i, n) for(int i=0; i<(n); ++i)
#define RED(i, n) for(int i=(n)-1; i>=0; --i)
#define MASK(i) (1LL << (i))
#define BIT(S, i) (((S) >> (i)) & 1)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define task "icebear"
/*END OF TEMPLATE. ICEBEAR AND THE CAT WILL WIN VOI26 */
 
const int MOD = 1e9 + 7;
const int inf = 1e9 + 27092008;
const ll INF = 1e18 + 27092008;
const int N = 2e5 + 5;
int numBall, f[N], ft[N];
iii ball[N];
vector<int> ans[N], compress;
 
void update(int x, int val) {
    for(; x; x -= x & -x) maximize(ft[x], val);
}
 
int get(int x) {
    int ans = 0;
    for(; x <= numBall; x += x & -x) maximize(ans, ft[x]);
    return ans;
}
 
void init(void) {
    cin >> numBall;
    FOR(i, 1, numBall) {
        cin >> ball[i].fi.fi >> ball[i].fi.se;
        ball[i].se = i;
        compress.pb(ball[i].fi.se);
    }
}
 
void process(void) {
    sort(ball + 1, ball + numBall + 1, [&](const iii &x, const iii &y){return (x.fi.fi < y.fi.fi) || (x.fi.fi == y.fi.fi && x.fi.se > y.fi.se);});
    sort(all(compress));
    compress.resize(unique(all(compress)) - compress.begin());
    FOR(i, 1, numBall) ball[i].fi.se = upper_bound(all(compress), ball[i].fi.se) - compress.begin();
 
    FOR(i, 1, numBall) {
        f[i] = get(ball[i].fi.se) + 1;
        update(ball[i].fi.se, f[i]);
    }
 
    int max_ans;
    cout << (max_ans = *max_element(f + 1, f + numBall + 1)) << '\n';
    FOR(i, 1, numBall) ans[f[i]].push_back(ball[i].se);
    FOR(i, 1, max_ans) {
        cout << ans[i].size() << ' ';
        for(int x : ans[i]) cout << x << ' ';
        cout << '\n';
    }
}
 
int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    int tc = 1;
//    cin >> tc;
    while(tc--) {
        init();
        process();
    }
    return 0;
}
 
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