#include<bits/stdc++.h>
#define rep(i, x) for(ll i = 0; i < x; i++)
#define rep2(i, x) for(ll i = 1; i <= x; i++)
#define all(a) (a).begin(),(a).end()
using ll = long long;
using ld = long double;
using namespace std;
signed main() {
	ld n, m, ans = 0; cin >> n >> m;
	ld bo = (n + 1) * m;
	rep(i, n + 1) {
		ans += (1 / bo) * (i * m);
	}
	cout << ans << endl;
	return 0;
}