#include <bits/stdc++.h>
using namespace std;

ifstream fin("litere.in");
ofstream fout("litere.out");

int a[100004],b[100004], m,n;
long long nr;
char ch;

void Intercls(int st, int m, int dr)
{
    int i, j, k;
    k = st;
    i = 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);
        Intercls(st, m, dr);
    }
}

int main()
{
    int i;
    fin>>n;
    for(i=1; i<=n; i++)
    {
        fin>>ch;
        a[i]=(int)ch;
    }

    Mergesort(1,n);
    fout<<nr;
    return 0;
}