#include<stdio.h>
#include<cstring>
const int maxn=100001;
long long pre[4][maxn];
char ch[10]="$cow";
char s[maxn];
int n;
long long ans;
int main()
{
	freopen("cowa.in","r",stdin);
	freopen("cowa.out","w",stdout);
	scanf("%d",&n);
	scanf("%s",s);
	int l=strlen(s);
	for(int i=l-1;i>=0;i--)
	{
		pre[3][i]=pre[3][i+1];
		if(s[i]==ch[3]) pre[3][i]++;
	}
	for(int i=l-1;i>=0;i--)
	{
		pre[2][i]=pre[2][i+1];
		if(s[i]==ch[2]) pre[2][i]+=pre[3][i+1];
	}
	for(int i=0;i<l;i++)
	 if(s[i]==ch[1]) ans+=pre[2][i+1];
	printf("%lld",ans);
}