#include <bits/stdc++.h>

using namespace std;
ifstream fin("litere.in");
ofstream fout("litere.out");
char a[100001], b[100001];
long long cnt;
void Interclasare(int st, int mij, int dr)
{
    int i, j, k;
    i = k = st;
    j = mij + 1;
    while(i <= mij && j <= dr)
    {
        if(a[i] <= a[j])
            b[k++] = a[i++];
        else {b[k++] = a[j++];cnt += (mij - i + 1);}
    }
    while(i <= mij)
        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 mij = (st + dr) / 2;
        MergeSort(st, mij);
        MergeSort(mij + 1, dr);
        Interclasare(st, mij, dr);
    }
}

int main()
{
    int i, n;
    fin >> n;
    fin.get();
    for(i = 1;i <= n;++i)
        fin >> a[i];
    MergeSort(1, n);
    fout << cnt << "\n";
    fout.close();
    return 0;
}