#include <bits/stdc++.h>
using namespace std;
int a[100004],b[100004], m,n;
long long nr;
char ch;
ifstream fin("litere.in");
ofstream fout("litere.out");
int Pivot(int st, int dr)
{
    int i,p,j=st;
    swap(a[st],a[(st+dr)/2]);
    p=a[st];
    for(i=st+1; i<=dr; i++)
        if(a[i]<p)
        {
            j++;
            swap(a[j],a[i]);
        }
    swap(a[st],a[j]);
    return j;
}
int Q(int st, int dr)
{
    int p=Pivot(st,dr);
    if(p-st>1) Q(st,p-1);
    if(dr-p>1) Q(p+1,dr);
}
void Intercl(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);
        Intercl(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;
}