#include <iostream>
#include <fstream>

using namespace std;

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

int main()
{
    int n,s=0,i,j,aux;
    char v[10000];
    f>>n;
    for (i=1;i<=n;i++)
        for (j=1;j<i;j++)
           if (v[i]<v[j])
             {
                 ++s;
                 aux=v[i];
                 v[i]=v[j];
                 v[j]=aux;
             }
    g<<s;
    return 0;
}