#include <iostream>
#include <fstream>

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

int n, k=0;
char v[10001];

int main() {
    fin >> n;
    for (int i=1; i<=n; i++){
        fin >> v[i];
    }
    int p=1;
    while (p<=n){
        int mini=v[p]-'0', poz=0;
        for (int i=p+1; i<=n; i++){
            if (mini > v[i]-'0'){
                mini = v[i]-'0';
                poz = i;
            }
        }
        if (mini!=v[p]-'0') {
            for (int i = poz; i > p; i--) {
                swap(v[i], v[i - 1]);
                k++;
            }
        }
        p++;
    }
    fout << k;
    return 0;
}