#include <bits/stdc++.h>

using namespace std;

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

char a[10003], b[10003];
int n, k, nrschimb;

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

void Merge(int st, int m, int dr)
{
    int i, j;
    k = 0;
    i = st; j = m + 1;
    while(i <= m && j <= dr)
    {
        if(a[i] > a[j])
        {
            b[++k] = a[j++];
            nrschimb += m - i + 1;
        }
        else
            b[++k] = a[i++];
    }
    while(i <= m) b[++k] = a[i++];
    while(j <= dr) b[++k] = a[j++];
    j = 1;
    for(i = st;i <= dr;i++)
        a[i] = b[j++];
}

void Sch(int p, int q)
{
    if(a[p] > a[q])
    {
        swap(a[p],a[q]);
        nrschimb++;
    }
}

void DI(int st, int dr)
{
    if(dr - st <= 1)
        Sch(st, dr);
    else
    {
        int mij = (st + dr) / 2;
        DI(st, mij);
        DI(mij + 1, dr);
        Merge(st, mij, dr);
    }
}

int main()
{
    Citire();
    DI(1, n);
    fout << nrschimb;
    fin.close();
    fout.close();
    return 0;
}