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

ifstream fin("litere.in");
ofstream fout("litere.out");
/**
5
4 2 5 1 3
*/
char a[100005];
int n;
char b[100005];
int nr;
void Inter(int st, int m, int dr)
{
    int i, k, j;
    i = st; j = m + 1;
    k = st;
    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)
{
    int m = (st + dr) / 2;
    if (dr - st >= 1)
    {
        MergeSort(st, m);
        MergeSort(m + 1, dr);
        Inter(st, m, dr);
    }
}
int main()
{
    int i;
    fin >> n;
    for (i = 1; i <= n; i++)
        fin >> a[i];
    MergeSort(1, n);
    fout << nr << " ";
    return 0;
}