/*
ID: wtfalex2
LANG: C++14
PROB: castle
//9cz2b944
*/
#define _CRT_SECURE_NO_WARNINGS
#pragma comment(linker, "/STACK:259000000")

#include <iostream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <ctime>
#include <map>
#include <set>
#include <string>
#include <queue>
#include <deque>
#include <cassert>
#include <cstdlib>
#include <bitset>
#include <algorithm>
#include <string>
#include <list>
#include <fstream>
#include <cstring>
#include <climits>
#include <stack>
#include <unordered_map>
#include <unordered_set>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef pair<string, int> psi;
typedef vector<string> vs;
typedef pair<ll, ll> pll;
typedef vector<ll> vll;
typedef vector<char> vc;
typedef vector<pii> vpii;
typedef vector<pair<ll, ll> > vpll;
typedef long double ld;

#define forn(i, n) for (int i = 0; i < (int)n; i++)
#define for1(i, n) for (int i = 1; i <= (int)n; i++)
#define forq(i, s, t) for (int i = s; i <= t; i++)
#define ford(i, s, t) for (int i = s; i >= t; i--)
#define mk make_pair
#define inb push_back
#define outb pop_back
#define all(v) v.begin(), v.end()
#define X first
#define Y second
#define TIME clock() * 1.0 / CLOCKS_PER_SEC
#define sqr(x) (x) * (x)
//#define double long double
#define y1 amdknkgsdaasdwapgnpikn
//
#define mp make_pair
#define pb push_back
#define XX first
#define YY second
//

const ld EPS = 1e-9;
const ld pi = acos(-1.0);

const int MAXN = (int)1e5 + 7;
const ll INF = 2e9 + 7;
const ll LINF = (ll)7e18;
const ll MOD = (ll)1e9 + 7;
const int CHASH = (ll)239017;
const ld DINF = (ld)1000000000000000.0;

void mkfile();
int solve();

int main()
{
#define TASK "rblock"
#ifdef _DEBUG
	mkfile();
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
	freopen("test.txt", "w", stderr);
	ld tstart = TIME;
	srand(2299);
#else
	//freopen(TASK".in", "r", stdin), freopen(TASK".out", "w", stdout);
	//freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout), freopen("test.txt", "w", stderr);
	srand(2299);
#endif
	solve();
#ifdef _DEBUG
	ld tend = TIME;
	cerr << tend - tstart << " s.\n";
#endif
	return 0;
}

void mkfile()
{
	freopen("input.txt", "a+", stdout);
	srand(time(0));
	return;
}

bool equal(double a, double b)
{
	return abs(a - b) < EPS;
}

int n, m, s, f, r;
int ds[MAXN], d[MAXN], dp[MAXN];
vi gs[MAXN], g[MAXN];
int was[MAXN];

void bfss()
{
	queue<int> q;
	q.push(s);
	ds[s] = 0;
	while (!q.empty())
	{
		int u = q.front();
		q.pop();
		for (auto to : gs[u])
		{
			if (ds[to] == INF)
			{
				ds[to] = ds[u] + 1;
				q.push(to);
			}
		}
	}
}

void dfsup(int u)
{
	was[u] = 1;
	for (auto to : gs[u])
	{
		if (ds[u] - 1 == ds[to])
		{
			g[u].inb(to);
			g[to].inb(u);
			if (!was[to])
				dfsup(to);
		}
	}
}

void bfsr()
{
	queue<int> q;
	q.push(r);
	was[r] = 1;
	d[r] = 0;
	while (!q.empty())
	{
		int u = q.front();
		q.pop();
		for (auto to : gs[u])
		{
			if (!was[to])
			{
				d[to] = d[u] + 1;
				was[to] = 1;
				q.push(to);
			}
		}
	}
}

void calcdp()
{
	queue<int> q;
	q.push(s);
	was[s] = 1;
	while (!q.empty())
	{
		int u = q.front();
		q.pop();
		int mxval = -1;
		int f = 0;
		for (auto to : g[u])
		{
			if (ds[to] + 1 == ds[u])
			{
				mxval = max(mxval, dp[to]);
				f = 1;
			}
			if (ds[to] - 1 == ds[u])
			{
				if (!was[to])
				{
					was[to] = 1;
					q.push(to);
				}
			}
		}
		if (f)
			dp[u] = min(mxval, dp[u]);
	}
}

int solve()
{
	scanf("%d %d", &n, &m);
	forn(i, m)
	{
		int x, y;
		scanf("%d %d", &x, &y);
		--x, --y;
		gs[x].inb(y), gs[y].inb(x);
	}
	scanf("%d %d %d", &s, &f, &r);
	--s, --f, --r;
	fill(ds, ds + n, INF);
	fill(d, d + n, INF);
	bfss();
	memset(was, 0, sizeof(was));
	dfsup(f);
	memset(was, 0, sizeof(was));
	bfsr();
	memset(was, 0, sizeof(was));
	forn(i, n)
		dp[i] = d[i];
	calcdp();
	printf("%d\n", dp[f]);
	return 0;
}