// Hey there.. I love you <3
#include <bits/stdc++.h>

using namespace std;
using ll = long long;

mt19937 rnd(time(nullptr));

const int N = 5e3 + 5, mod = 1e9 + 7;
const double pi = acos(-1);


void work() {
    
    int d, s, e;
    cin >> d >> s >> e;
    int out = d - s - e;
    double p = 1.0 / d, pOut = p * (d - s) / out;
    double ans = min(out, s) * pOut + max(0, s - out) * p;
    cout << fixed << setprecision(12) << ans << endl;
    
    
}


void init() {
    cin.tie(nullptr);
    istream::sync_with_stdio(false);
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);


}

int main() {
    init();
    
    int testCases = 1;
//    cin >> testCases;
    while (testCases--) work();
    
    return 0;
}