#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef pair<int, ii> iii;
typedef pair<ii, int> ri3;
#define mp make_pair
#define pb push_back
#define fi first
#define sc second
#define SZ(x) (int)(x).size()
#define ALL(x) begin(x), end(x)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define FOR(i, a, b) for (int i = a; i <= b; ++i)
#define RFOR(i, a, b) for (int i = a; i >= b; --i)
const int MAXN = 2e5+5;
int N,M,S,D,A,B;
vector<int> al[MAXN];
int dS[MAXN], dD[MAXN], dA[MAXN], dB[MAXN];
void bfs(int x, int d[]) {
FOR(i,1,N) d[i] = -1;
queue<int> q;
d[x] = 0; q.push(x);
while (!q.empty()) {
int u = q.front(); q.pop();
for (auto v : al[u]) if (d[v] == -1) d[v] = d[u]+1, q.push(v);
}
}
int main() {
//freopen("in.txt", "r", stdin);
ios::sync_with_stdio(false);
cin.tie(0);
cin >> N >> M;
cin >> S >> D >> A >> B;
FOR(i,1,M){
int U, V; cin >> U >> V;
al[U].push_back(V);
al[V].push_back(U);
}
bfs(S, dS);
bfs(D, dD);
bfs(A, dA);
bfs(B, dB);
if (dS[A] > dD[A] || dS[B] > dD[B]) cout << -1 << '\n';
else {
int ans = min(dD[A]-dS[A], dD[B]-dS[B]);
int sS = S, sD = D;
FOR(i,1,N) {
if (dS[i] + dA[i] == dS[A] && dS[i] + dB[i] == dS[B]) sS = (dS[sS] > dS[i] ? sS : i);
if (dD[i] + dA[i] == dD[A] && dD[i] + dB[i] == dD[B]) sD = (dD[sD] > dD[i] ? sD : i);
}
//cout << ans << " :: " << sS << " " << sD << endl;
if (dS[A] == dS[B] && dD[A] == dD[B] && sS != sD && dS[sS] < dD[sD]-ans) ans -= 1;
cout << ans << '\n';
}
}
