#include<bits/stdc++.h>
using namespace std;
const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()
const int maxn = 2e5+10;
int n, m, a,b,s1,s2;
int d[maxn][5];
vector<int> g[maxn];
void bfs(int beg, int id) {
for(int i = 1; i <= n; i++) {
d[i][id] = inf;
}
d[beg][id] = 0;
queue<int> q; q.push(beg);
while(q.size()) {
int u = q.front();
q.pop();
for(auto v : g[u]) {
if(d[v][id] == inf) {
d[v][id] = d[u][id]+1;
q.push(v);
}
}
}
}
void solve() {
cin >> n >> m;
cin >> a >> b >> s1 >> s2;
for(int i = 1; i <= m; i++) {
int u,v; cin >> u >> v;
g[u].pb(v);
g[v].pb(u);
}
//bfs partindo de a e de b
bfs(a,1);
bfs(b,2);
bfs(s1,3);
bfs(s2,4);
if(d[a][3] == d[a][4] && d[b][3] == d[b][4]) {
//ve qual vai poder escolher para onde vai primeiro
int mna = inf;
int mnb = inf;
for(int i = 1; i <= n; i++) {
//a->i, i->b
if(d[i][1] + d[i][3] == d[a][3] && d[i][1] + d[i][4] == d[a][4]) {
mna = min(mna,d[i][3]);
}
if(d[i][2] + d[i][3] == d[b][3] && d[i][2] + d[i][4] == d[b][4]) {
mnb = min(mnb,d[i][3]);
}
}
cout << max(d[b][3]-d[a][3]-(mnb<mna),(int) -1) << endl;
}
else {
//o b vai pro menor dele e o a acompanha
cout << max(min(d[b][3]-d[a][3],d[b][4]-d[a][4]),(int) -1) << endl;
}
}
int32_t main() {
ios::sync_with_stdio(false); cin.tie(0);
// freopen("in.in", "r", stdin);
// freopen("out.out", "w", stdout);
int tt = 1;
// cin >> tt;
while(tt--) solve();
}
