#include<bits/stdc++.h>

using namespace std;
const int N=300300;
int n,m,a[N],deg[N][2],f[N][2],ans=(int)1e9;
queue<pair<int,int> > q;
vector<int> edge[N];
int main(){
	cin>>n>>m;
	for(int t=1;t<=n;t++){
        cin>>a[t];
    }
	for(int t=1;t<=m;t++){
		int u,v;
        cin>>u>>v;
		deg[u][a[v]]++;deg[v][a[u]]++;
		edge[u].push_back(v);edge[v].push_back(u);
	}
	for(int t=1;t<=n;t++){
		if(!deg[t][0]){
			f[t][0]=1;
			q.push({t,0});
		}
		if(!deg[t][1]){
			f[t][1]=1;
			q.push({t,1});
		}
	}
	while(!q.empty()){
		int u,Tag;
		tie(u,Tag)=q.front();q.pop();
		for(int t=0;t<edge[u].size();t++){
            int v=edge[u][t];
			if(a[v]==Tag){
                continue;
            }
			f[v][a[u]]=max(f[v][a[u]],f[u][Tag]+1);deg[v][a[u]]--;
			if(!deg[v][a[u]]){
                q.push({v,a[u]});
            }
		}
	}
	int tmp[4]={0,0,0,0};
	for(int t=1;t<=n;t++){
		for(int i=0;i<=1;i++){
			if(deg[t][i]){
                f[t][i]=(int)1e9;
            }
			tmp[a[t]+i*2]=max(tmp[a[t]+i*2],f[t][i]);
		}
    }
    for(int t=0;t<4;t++){
        ans=min(ans,tmp[t]);
    }
    ans++;
	if(ans<=(int)1e9){
        cout<<ans<<'\n';
    }
	else{
        cout<<"infinity"<<'\n';
    }
	return 0;
}