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

long long int d[200000000] = {};

void kansu( long long int n, long long int m, long long int s ) {

  if ( n == 0 ) {

    d[ s ]++;
    return;

  }

  for ( long long int i = 1; i <= m; i++ ) {
    kansu( n - 1, m, s + i );
  }

  return;

}

int main() {

  while( true ) {

    long long int n, m, k;
    cin >> n >> m >> k;
    if ( n == 0 ) break;

    long long int a = 1;
    for ( long long int i = 0; i < n; i++ ) {
      a *= m;
    }

    long long int ans = 0;

    for ( long long int i = 0; i <= n * m; i++ ) {
      d[i] = 0;
    }

    kansu( n, m, 0 );

    for ( long long int i = 1; i <= n * m; i++ ) {

      ans += d[ i ] * max( 1LL, i - k );

    }

    cout << setprecision(10) << 1.00 * ans / a << endl;

  }

  return 0;

}