#include<iostream>
#include<cmath>
#include<cstdio>
 
using namespace std;
 
long double denominator,ans;
int n,m,k;
 
void solve(int rev,int sum){
  if(rev){
    for(int i = 1; i <= m; i++)
      solve(rev-1,sum+i);
  }else{
    sum = max(1,sum-k);
    ans += (long double)sum/denominator;
  }
}
 
int main(){
 
  while(cin >> n >> m >> k && n+m+k){
    ans = 0;
    denominator = pow((double)m,(double)n);
    solve(n,0);
    printf("%.8Lf\n",ans);
  }
  return 0;
}