#include<bits/stdc++.h>
#define int long long
using namespace std;
#define fi first
#define sc second
#define pii pair<int,int>
#define pdd pair<double,double>
#define pb push_back
#define umap unordered_map
#define mset multiset
#define pq priority_queue
#define ull unsigned long long
#define i128 __int128
#define ld long double
#define fixs fixed<<setprecision
#define FileIn(x) freopen(x".in","r",stdin)
#define FileOut(x) freopen(x".out","w",stdout)
#define FileIO(x) FileIn(x),FileOut(x);
const int maxn=300+10;
int n,m,K;
ld fr[maxn],res;
void solve(){
    cin>>n>>m>>K;
    // fr[0]=1;
    // for(int i=1;i<=m;i++) fr[i]=fr[i-1]*i;
    for(int i=1;i<=m;i++) fr[i]=fr[i-1]+log2(i);
    for(int i=1;i<=n;i++){
        for(int j=0;j<=m;j++){
            for(int k=0;k<=m;k++){
                if(!(j+k<=m&&j<K&&j+k>=K)) continue;
                // res+=i*fr[m]*pow(n-i,j)*pow(i-1,m-j-k)/fr[j]/fr[k]/fr[m-j-k]/pow(n,m);
                ld x=log2(i)+fr[m]+(i<n?log2(n-i)*j:0)+(i>1?log2(i-1)*(m-j-k):0)-fr[j]-fr[k]-fr[m-j-k]-log2(n)*m;
                // cout<<i<<" "<<j<<" "<<k<<" "<<pow(i-1,m-j-k)<<endl;
                // cout<<i*fr[m]*pow(n-i,j)*pow(i-1,m-j-k)/fr[j]/fr[k]/fr[m-j-k]/pow(n,m)<<endl;
                if((i==n&&j!=0)||(i==1&&j+k!=m)) continue;
                res+=pow(2,x);
            }
        }
    }
    cout<<fixs(10)<<res<<endl;
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
    int t=1;
    // cin>>t;
    while(t--) solve();
    return 0;
}
/*
Samples
input:

output:

THINGS TODO:
检查freopen，尤其是后缀名
检查空间
检查调试语句是否全部注释
*/