#include<cstdio>
#include<cmath>
using namespace std;

typedef long double D;

int n,m,k,N;

D rec(int d,int sum){
  if(d==n){
    sum -= k;
    if(sum<1)sum = 1;
    return (D)sum/N;
  }

  D res = 0;
  for(int i=1;i<=m;i++)res += rec(d+1,sum+i);
  return res;
}

int main(){
  while(scanf("%d%d%d",&n,&m,&k),n+m+k){
    N = pow(m,n);
    printf("%.9Lf\n",rec(0,0));
  }
}
    