// Author: YE Minghan
#include<bits/stdc++.h>
using namespace std;
#ifdef DEBUG
#include "templates/debug.h"
#define __int128 ll
#else
#define dbg(...) (void)0
#define msg(...) (void)0
#endif
#define ll long long
#define endl '\n'
#define PB emplace_back
#define PPB pop_back
#define MP make_pair
#define ALL(Name) Name.begin(),Name.end()
#define PII pair<int,int>
#define VI vector<int>
#define GI greater<int>
#define fi first
#define se second

const int N=300005;
int n,m;
bool a[N];
int f[2][N],d[2][N]; // 0:diff 1:same
VI g[N];

int main()
{
	ios::sync_with_stdio(false),cin.tie(nullptr);
//	int _;cin>>_;while(_--)

	cin>>n>>m;
	for(int i=1;i<=n;i++)cin>>a[i];
	for(int i=1,u,v;i<=m;i++)
	{
		cin>>u>>v,g[u].PB(v),g[v].PB(u);
		d[a[v]][u]++,d[a[u]][v]++;
	}
	queue<pair<bool,int>>q;
	memset(f,0xc0,sizeof(f));
	for(int i=1;i<=n;i++)
		for(int j=0;j<=1;j++)
			if(!d[j][i])f[j][i]=1,q.emplace(j,i);
	int cnt=0;
	while(!q.empty())
	{
		auto [p,x]=q.front();q.pop();
		++cnt;
		for(int y:g[x])
		{
			if(p==a[y])continue;
			f[a[x]][y]=max(f[a[x]][y],f[p][x]+1);
			if(!--d[a[x]][y])q.emplace(a[x],y);
		}
	}
	if(cnt<n<<1)return puts("infinity"),0;
	int ans=2e9;
	for(int i=0;i<4;i++)
	{
		int mx=1;
		for(int j=1;j<=n;j++)
			if((i>>1)^a[j])mx=max(mx,f[i&1][j]+1);
		ans=min(ans,mx);
	}
	cout<<ans;

	return 0;
}