#include <bits/stdc++.h>
using namespace std;
ifstream fin("litere.in");
ofstream fout("litere.out");
char a[100003], b[100003];
int nr;
void Interclasare(int st,int m, int dr)
{
    int j,k,i;
    i = st;
    k = st;
    j = m+1;
   while( i <= m && j <= dr)
        if ( a[i] > a[j])
           {
            b[k ++] = a[j++];
            nr +=(m-i+1);
           }
        else b[k++] = a[i++];
    while ( i <= m)  b[k++] = a[i++];
    while ( j <= dr) b[k++] = a[j++];
    for(i = st;i <= dr; i ++)
        a[i] = b[i];
}
void Mergesort(int st,int dr)
{
    if ( dr - st >= 1)
    {
        int m = (st+dr)/2;
        Mergesort(st,m);
        Mergesort(m+1,dr);
        Interclasare(st,m,dr);
    }
}
int main()
{
    int i,n;
    fin >> n;
    for ( i = 1; i <= n; i++)
        fin >> a[i];
    Mergesort(1,n);
    fout << nr;
    return 0;
}