Example

Input

3 3 1 2 4
1 2
2 3
3 1


Output

IMPOSSIBLE
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <set>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstdio>
#include <cstring>
#include <iterator>
#include <bitset>
#include <unordered_set>
#include <unordered_map>
#include <fstream>
#include <iomanip>
#include <cassert>
//#include <utility>
//#include <memory>
//#include <functional>
//#include <deque>
//#include <cctype>
//#include <ctime>
//#include <numeric>
//#include <list>
//#include <iomanip>

//#if __cplusplus >= 201103L
//#include <array>
//#include <tuple>
//#include <initializer_list>
//#include <forward_list>
//
//#define cauto const auto&
//#else

//#endif

using namespace std;


typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef vector<int> vint;
typedef vector<vector<int> > vvint;
typedef vector<long long> vll, vLL;
typedef vector<vector<long long> > vvll, vvLL;

#define VV(T) vector<vector< T > >

template <class T>
void initvv(vector<vector<T> > &v, int a, int b, const T &t = T()){
    v.assign(a, vector<T>(b, t));
}

template <class F, class T>
void convert(const F &f, T &t){
    stringstream ss;
    ss << f;
    ss >> t;
}

#undef _P
#define _P(...) (void)printf(__VA_ARGS__)
#define reep(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n) reep((i),0,(n))
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define F first
#define S second
#define mkp make_pair
#define RALL(v) (v).rbegin(),(v).rend()
#define DEBUG
#ifdef DEBUG
#define dump(x)  cout << #x << " = " << (x) << endl;
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
#else
#define dump(x) 
#define debug(x) 
#endif

#define MOD 1000000007LL
#define EPS 1e-8
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
#define maxs(x,y) x=max(x,y)
#define mins(x,y) x=min(x,y)

bool dp[55][55][110];


void mainmain(){
	int n,m;
	vint a(3);
	cin>>n>>m;
	rep(i,3) cin>>a[i];
	rep(i,m){
		int a,b;
		cin>>a>>b;
		a--;
		b--;
		dp[a][b][1]=true;
	}
	reep(o,2,110){
		rep(k,n){
			rep(i,n){
				rep(j,n){
					if(dp[i][k][1]&&dp[k][j][o-1]) dp[i][j][o]=true;
					if(dp[i][k][o-1]&&dp[k][j][1]) dp[i][j][o]=true;
				}
			}
		}
	}
	vector<bool> v(n);
	v[n-1]=true;
	VV(bool) vv;
	initvv(vv,n,3);
	rep(i,3){
		rep(j,n){
			if(dp[j][n-1][a[i]]) vv[j][i]=true;
		}
	}
	bool update=true;
	int cnt=1;
	while(update){
		update=false;
		queue<int> q;
		rep(i,n){
			if(v[i]) continue;
			bool ok=true;
			rep(j,3){
				if(!vv[i][j]) ok=false;
			}
			if(ok){
				update=true;
				q.push(i);
			}
		}
		while(q.size()){
			int i=q.front();
			q.pop();
			v[i]=true;
			rep(j,3){
				rep(k,n){
					if(dp[k][i][a[j]]) vv[k][j]=true;
				}
			}
		}
		if(v[0]){
			cout<<cnt<<endl;
			return;
		}
		cnt++;
	}
	cout<<"IMPOSSIBLE"<<endl;
}


signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout<<fixed<<setprecision(20);
    mainmain();
}