#include <iostream>
#include <fstream>
using namespace std;

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

   int main()
{
	int n, i, j, cnt = 0;
	char v[10001];
	cin >> n ;


	for ( i = 1; i < n; i++) {
	   for ( j = 0; j < i; j++) {
			if (v[j] > v[i]) { swap (v[i],v[j]);
				           cnt++;
			                  }
		}
	}

	cout << cnt;

	return 0;
}