int main() {
#ifndef ONLINE_JUDGE
freopen("input.txt", "r", stdin);
#endif
int n;
int m;
scanf("%d%d", &n, &m);
TGraph g;
g.resize(n);
for (int i = 0; i < m; ++i) {
int begin;
int end;
scanf("%d%d", &begin, &end);
--begin;
--end;
g[begin].push_back(end);
g[end].push_back(begin);
}
int s;
int f;
int r;
scanf("%d%d%d", &s, &f, &r);
--s;
--f;
--r;
TLine sDist;
DFS(g, s, &sDist);
TLine rDist;
DFS(g, r, &rDist);
TLine cache(n, -1);
cache[s] = rDist[s];
TrackMaxDist(g, sDist, rDist, f, &cache);
printf("%d\n", cache[f]);
return 0;
}
