#include<algorithm>
#include<iostream>
#include<vector>
#include<cstdio>
#include<set>
using namespace std;
#define ll long long
#define For(i,l,r) for(int i=l;i<=r;i++)
#define FOR(i,l,r) for(int i=l;i>=r;i--)
#define MAXN 200001
int N,M,a[MAXN],u[MAXN],v[MAXN],deg[MAXN][2];
int get(){int x=0,f=1;char c=getchar();while(c<'0'||c>'9')c=='-'&&(f=-1),c=getchar();while(c>='0'&&c<='9')x=x*10+c-'0',c=getchar();return x*f;}
int main()
{
	while(cin>>N>>M)
	{
		string s;cin>>s;For(i,1,N)a[i]=s[i-1]=='b';For(i,1,N)deg[i][0]=deg[i][1]=0;For(i,1,M)u[i]=get(),v[i]=get();
		For(i,1,M)deg[u[i]][a[v[i]]]++,deg[v[i]][a[u[i]]]++;
		ll ans=0;For(i,1,M)if(a[u[i]]!=a[v[i]])ans+=1ll*(deg[u[i]][a[v[i]]]-1)*(deg[v[i]][a[u[i]]]-1);
		cout<<ans<<'\n';
	}
}