#include<bits/stdc++.h>
using namespace std;
const int N=3e5+5;
const int inf=1e9+7;
int n,m,a[N],f[N<<1],dg[N<<1];
vector<int> edge[N<<1];
void lk(int x,int y)
{edge[x].push_back(y),dg[y]++;}

int main()
{
    ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    cin>>n>>m;for(int i=1;i<=n;i++)cin>>a[i];
    for(int i=1;i<=m;i++)
    {
        int x,y;cin>>x>>y;
        if(a[x]==a[y])lk(x+n,y),lk(y+n,x);
        else lk(x,y+n),lk(y,x+n);
    }fill(f+1,f+n*2+1,inf);queue<int> q;
    for(int i=1;i<=2*n;i++)
    if(!dg[i])f[i]=1,q.push(i);
    while(!q.empty())
    {
        int u=q.front();q.pop();
        for(int v:edge[u])
        {
            dg[v]--;
            if(f[v]==inf)f[v]=f[u]+1;
            f[v]=max(f[v],f[u]+1);
            if(!dg[v])q.push(v);
        }
    }int x=0,y=0,z=0,w=0;
    for(int i=1;i<=n;i++)
    if(a[i])x=max(x,f[i]),y=max(y,f[i+n]);
    else z=max(z,f[i]),w=max(w,f[i+n]);
    int ans=min({x,y,z,w})+1;
    if(ans>=inf)cout<<"infinity\n";
    else cout<<ans<<'\n';
    return 0;
}