Example

Input

3 3 1 2 4
1 2
2 3
3 1


Output

IMPOSSIBLE
#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
using namespace std;
typedef long long ll;
typedef unsigned long long ul;
typedef unsigned int ui;
const ll mod = 1000000007;
typedef double ld;
typedef complex<ld> Point;
const ll INF = mod * mod;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
const ld eps = 1e-6;
const ld pi = acos(-1.0);
typedef pair<ld, ld> LDP;
typedef pair<ll, ll> LP;

const int mn = 20000;
bool exi[50][101][50];
vector<int> G[50];

int num[3];
int n;
bool visit[mn][50];
int ans[mn][50];
int dfs(int x,int t) {
	if (x == n - 1)return 0;
	if (t >= mn)return mod;
	if (visit[t][x])return ans[t][x];
	visit[t][x] = true;
	int ret = 0;
	rep(i, 3) {
		int cret = mod;
		rep(j, n) {
			if (exi[x][num[i]][j]) {
				cret = min(cret, dfs(j, t + num[i]));
			}
		}
		ret = max(ret, cret);
	}
	return ans[t][x] = ret+1;
}


void solve(){
	int m; 
	cin >> n >> m;
	rep(i, 3)cin >> num[i];
	rep(i, m) {
		int a, b; cin >> a >> b; a--; b--;
		G[a].push_back(b);
	}
	rep(id, n) {
		exi[id][0][id] = true;
		rep(i, 100) {
			rep(j, n) {
				if (exi[id][i][j]) {
					rep(k, G[j].size()) {
						int to = G[j][k];
						exi[id][i + 1][to] = true;
					}
				}
			}
		}
	}
	int out = dfs(0,0);
	if (out >= mod) {
		cout << "IMPOSSIBLE" << endl;
	}
	else {
		cout << out << endl;
	}

}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	solve();
	//stop
		return 0;
}
