#include<bits/stdc++.h>
#define int long long
//#define int __int128
#define ll long long
#define pa pair<int,int>
//#define int unsigned long long
#define sg signed
#define fi first
#define se second
#define ls s[x][0]
#define rs s[x][1]
#define ld long double
#define bs basic_string
const int inf=1e18;
using namespace std;
inline int read(){
    int s=0,w=1;
    char ch=getchar();
    while(ch<'0'||ch>'9') {
        if(ch=='-')w=-1;
        ch=getchar();
    }
    while(ch<='9'&&ch>='0')
        s=s*10+ch-'0',ch=getchar();
    return s*w;
}
int n,m,a[300005];
int in[300005][4];
int dp[300005][4];
queue<pa>q;
bs<int>v[300005];
int ans[4];
void solve(){
	n=read(),m=read();
	for(int i=1;i<=n;i++)a[i]=read();
	for(int i=1;i<=m;i++){
		int x=read(),y=read();
		v[x]+=y;
		v[y]+=x;
		for(int j=0;j<4;j++)in[x][j]++,in[y][j]++;
	}
	for(int i=1;i<=n;i++){
		if(!a[i]){
			dp[i][2]=dp[i][3]=1;in[i][2]=in[i][3]=0;
			dp[i][0]=dp[i][1]=2;
			q.push({i,2});q.push({i,3});
		}else{
			dp[i][0]=dp[i][1]=1;in[i][0]=in[i][1]=0;
			dp[i][2]=dp[i][3]=2;
			q.push({i,0});q.push({i,1});
		}
	}
	while(!q.empty()){
		int x=q.front().fi,op=q.front().se;
		q.pop();
		int op1=(op+1)%4;
		for(auto y:v[x]){
			if(in[y][op1]==0)continue;
			dp[y][op1]=max(dp[y][op1],dp[x][op]+1);
			in[y][op1]--;
			if(!in[y][op1])q.push({y,op1});
		}
	}
	int cnt=0;
	for(int i=0;i<4;i++){
		bool ok=0;
		for(int j=1;j<=n;j++)if(in[j][i]>0)ok=1;
		cnt+=ok;
	}
	if(cnt==4){
		printf("infinity");
		return;
	}
	for(int i=1;i<=n;i++)for(int j=0;j<4;j++)ans[j]=max(ans[j],dp[i][j]);
//	for(int i=0;i<4;i++)cout<<i<<" "<<ans[i]<<endl;
	printf("%lld\n",min(min(ans[0],ans[1]),min(ans[2],ans[3])));
}
signed main(){
	int t=1;while(t--)solve();
    return 0;
}