#include<cstdio>
#include<algorithm>
using namespace std;
const int L_N=1e5+10;
typedef long long LL;
LL f[L_N][3];
int N;
char str[L_N];
int main(){
	freopen("cowa.in","r",stdin);
	freopen("cowa.out","w",stdout);
	scanf("%d",&N);
	scanf("%s",str+1);
	
	for(int i=1;i<=N;i++){
		f[i][0]=f[i-1][0];
		f[i][1]=f[i-1][1];
		f[i][2]=f[i-1][2];
		if(str[i]=='C'){
			f[i][0]+=1;
		}else if(str[i]=='O'){
			f[i][1]+=f[i-1][0];
		}else if(str[i]=='W'){
			f[i][2]+=f[i-1][1];
		}
	}
	printf("%lld\n",f[N][2]);
	
	return 0;
}