#include <bits/stdc++.h>
using namespace std;
template<class T, class U>
void ckmin(T &a, U b)
{
if (a > b) a = b;
}
template<class T, class U>
void ckmax(T &a, U b)
{
if (a < b) a = b;
}
#define MP make_pair
#define PB push_back
#define LB lower_bound
#define UB upper_bound
#define fi first
#define se second
#define SZ(x) ((int) (x).size())
#define ALL(x) (x).begin(), (x).end()
#define FOR(i, a, b) for (auto i = (a); i < (b); i++)
#define FORD(i, a, b) for (auto i = (a) - 1; i >= (b); i--)
#define MAXN 200013
#define INF 1000000007
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<pii> vpi;
typedef vector<pll> vpl;
int N, M, S, T, A, B;
vi edge[MAXN];
vi ds, dt, da, db;
int dis[MAXN];
int ans;
void bfs(int s, vi &dist)
{
FOR(i, 0, N) dist[i] = INF;
queue<int> q; q.push(s); dist[s] = 0;
while(!q.empty())
{
int u = q.front(); q.pop();
for (int v : edge[u])
{
if (dist[v] > dist[u] + 1)
{
dist[v] = dist[u] + 1;
q.push(v);
}
}
}
}
bool check(int x)
{
queue<int> q;
FOR(i, 0, N)
{
if (dt[i] <= x)
{
dis[i] = 0;
q.push(i);
}
else dis[i] = INF;
}
//they start at T, you start at S.
//they need to be able to reach A or B at least one second before you.
// if (dis[A] == 0 || dis[B] == 0) return false;
while(!q.empty())
{
int u = q.front(); q.pop();
for (int v : edge[u])
{
//can i go to v?
if (dis[v] > dis[u] + 1 && ds[v] > dis[u] + 1)
{
dis[v] = dis[u] + 1;
q.push(v);
}
}
}
return (dis[A] == INF && dis[B] == INF);
//they can start at any place marked ok.
//they go, then you go.
}
int32_t main()
{
cout << fixed << setprecision(12);
cerr << fixed << setprecision(4);
ios_base::sync_with_stdio(false); cin.tie(0);
cin >> N >> M >> S >> T >> A >> B; S--; T--; A--; B--;
assert(S != A && S != B && T != A && T != B);
FOR(i, 0, M)
{
int u, v;
cin >> u >> v;
u--; v--;
edge[u].PB(v);
edge[v].PB(u);
}
ds.resize(N); dt.resize(N); da.resize(N); db.resize(N);
bfs(S, ds);
bfs(T, dt);
bfs(A, da);
bfs(B, db);
int lo = 0, hi = N + 1;
while(hi > lo)
{
int mid = (hi + lo + 1) >> 1;
if (check(mid)) lo = mid;
else hi = mid - 1;
}
ans = lo - 1;
cout << ans << '\n';
return 0;
}
