#include<stdio.h>
char a[10001];
long n,i,j,k,fr[100];

int main(){

freopen("litere.in","r",stdin);
freopen("litere.out","w",stdout);

scanf("%ld",n);

for(i=0;i<n;i++)
	 {
	  scanf("%ld",a[i]);

	  fr[a[i]-'a']=fr[a[i]-'a']+1;

	  for(j=0;j<fr[a[i]-'a'];j++)

			 k=k+fr[a[j]-'a'];
	  }

printf("%ld",k-1);
return 0;
}