#include<iostream>#include<stdio.h>#include<cstring>#include<math.h>#include<cmath>using namespace std;int dp[2][100000008];int main(){int n,m,x,sum,i,j,k;while(scanf("%d%d%d",&n,&m,&k)!=EOF){if(n==0&&m==0&&k==0)break;sum=n*m;for(i=0;i<=sum;i++){dp[0][i]=0;dp[1][i]=0;}for(i=1;i<=m;i++)dp[1][i]=1;for(i=2;i<=n;i++){for(j=0;j<=sum;j++)dp[i%2][j]=0;for(x=sum;x>=1;x--){for(j=1;j<=m&&j<x;j++)dp[i%2][x]=dp[i%2][x]+dp[1-i%2][x-j];}}double all;all=pow((double)m,(double)n);double ans=0.0;for(i=1;i<=k;i++)ans=ans+(double)dp[n%2][i];for(i=k+1;i<=sum;i++)ans=ans+(double)(i-k)*dp[n%2][i];printf("%.8lfn",ans/all);}return 0;}
