#include <bits/stdc++.h>

using namespace std;

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

int main()
{
    int n,i=0,k=0,sw,j=n-1;
    char v[10000];
    in>>n;
    in>>v;
    do
    {
        sw=1;
        i=0;
        j=n-1;
        while(i<j)
        {
            if(v[i]>v[i+1])
                swap(v[i],v[i+1]),sw=0,k++;
            i++;
            if(v[j]<v[j-1])
                swap(v[j],v[j-1]),sw=0,k++;
            j--;
        }

    }while(sw==0);
    out<<k;
    return 0;
}