#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<vector>
#include<queue>
#include<algorithm>
#include<string>
#include<sstream>
#include<cctype>
#include<cmath>
#include<iomanip>
#include<map>
#include<stack>
#include<set>
#include<functional>
#define in(x) x=read()
#define qr read()
#define int ll
#define mp make_pair
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
namespace fastIO
{
    #define BUF_SIZE 100000
    bool IOerror=0;
    inline char nc()
	{
        static char buf[BUF_SIZE],*p1=buf+BUF_SIZE,*pend=buf+BUF_SIZE;
        if (p1==pend){
            p1=buf; pend=buf+fread(buf,1,BUF_SIZE,stdin);
            if (pend==p1){IOerror=1;return -1;}
        }
        return *p1++;
    }
    inline bool blank(char ch){return ch==' '||ch=='\n'||ch=='\r'||ch=='\t';}
    inline ll read()
	{
        bool sign=0; char ch=nc();ll x=0;
        for (;blank(ch);ch=nc());
        if (IOerror)return 0;
        if (ch=='-')sign=1,ch=nc();
        for (;ch>='0'&&ch<='9';ch=nc())x=x*10+ch-'0';
        if (sign)x=-x;
        return x;
    }
    #undef BUF_SIZE
};
using namespace fastIO;
int num[1000010][2],s[1000010],u[1000010],v[1000010];
signed main()
{
	//freopen(".in","r",stdin);
	//freopen(".out","w",stdout);
	int n,m;
	while(cin>>n>>m)
	{
		for(int i=1;i<=n;i++)
		{
			char ch=getchar();
			for(;!isalpha(ch);ch=getchar());
			s[i]=ch=='o';
			num[i][0]=num[i][1]=0;
		}
		for(int i=1;i<=m;i++)
		{
			int x,y;
			cin>>x>>y;
			// cout<<x<<' '<<y<<endl;
			num[y][s[x]]++,num[x][s[y]]++;
			u[i]=x,v[i]=y;
		}
		int ans=0;
		for(int i=1;i<=m;i++)
		{
			if(s[v[i]]<s[u[i]])swap(u[i],v[i]);
			if(s[u[i]]==0&&s[v[i]]==1)ans+=(num[u[i]][1]-1)*(num[v[i]][0]-1);
		}
		cout<<ans<<'\n';
	}
	return 0;
}