#include<stdio.h>
#define N 10005
int n, suma=0, i, j, w[N],sumafinala=0;
char v[N];
const char in[]= "litere.in";
const char out[]= "litere.out";

int main()
{
	freopen(in,"r",stdin);
	freopen(out,"w",stdout);
	scanf("%d",&n);
	scanf("%s",v);
	for(i=0;i<n;++i, suma=0){
		for(j=i+1;j<=n;++j)
			if(v[i]>v[j])++suma;
			sumafinala+=suma;}
			printf("%d\n",sumafinala-n);
return 0;
}