#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
typedef long long LL;
const int SIZEN=100010;
int N;
char S[SIZEN];
LL f[SIZEN][3]={0};
void work(void){
	for(int i=1;i<=N;i++){
		memcpy(f[i],f[i-1],sizeof(f[i]));
		if(S[i]=='C'){
			f[i][0]++;
		}
		else if(S[i]=='O'){
			f[i][1]+=f[i-1][0];
		}
		else if(S[i]=='W'){
			f[i][2]+=f[i-1][1];
		}
	}
	cout<<f[N][2]<<endl;
}
int main(){
	freopen("cowa.in","r",stdin);
	freopen("cowa.out","w",stdout);
	scanf("%d",&N);
	scanf("%s",S+1);
	work();
	return 0;
}