#include <bits/stdc++.h>
using namespace std;
 
int main() {
	int a, b, c, f, m, n, p, r, s; vector<vector<int>> g; vector<int> d, h, v; queue<int> q;
	ios_base::sync_with_stdio(0), cin.tie(0), cin >> n >> m, p = n+1;
	for (g.resize(p), d.resize(p,-1), h.resize(p,0), v.resize(p,-1); m--; )
		cin >> a >> b, g[a].push_back(b), g[b].push_back(a);
	for (cin >> s >> f >> r, d[r] = 0, q.push(r); not q.empty(); q.pop())
		for (auto u: g[a = q.front()])
			if (d[u] == -1)
				d[u] = d[a]+1, q.push(u);
	for (h[s] = d[s], v[s] = 0, q.push(s); not q.empty(); q.pop())
		for (auto u: g[a = q.front()])
			if (b = v[a]+1, c = min(h[a],d[u]), v[u] == -1 or (v[u] >= b and c > h[u])) 
				if (v[u] = b, h[u] = c, u != f)
					q.push(u); 
	cout << h[f]; }
 

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