#include <bits/stdc++.h>

using namespace std;

const int N = 1e6 + 5;
typedef long long LL;
int a, b, c;
double f[105][105][105];

double dp(int nowa, int nowb, int nowc) {
    if (nowa >= 100 || nowb >= 100 || nowc >= 100) return 0;
    if (f[nowa][nowb][nowc]) return f[nowa][nowb][nowc];
    //cout << 1 << endl;
    int sum = nowa + nowb + nowc;
    return f[nowa][nowb][nowc] =
               1.0 + (1.0 * nowa / sum * dp(nowa + 1, nowb, nowc) +
                      1.0 * nowb / sum * dp(nowa, nowb + 1, nowc) +
                      1.0 * nowc / sum * dp(nowa, nowb, nowc + 1));
}

int main() {
    cin >> a >> b >> c;
    printf("%.10lf",dp(a, b, c));
    return 0;
}
#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <algorithm>
#include <math.h>
#include <vector>
#include <map>
#include <queue>
#include <limits.h>
#include <stack>
using namespace std;
typedef long long ll;
const int maxn = 110;
int H, W, A, B, ans = 0;
int nx, ny;
bool vis[20][20];
void solve(int s, int x, int y, int a, int b)
{
	if(s==H*W)
	{
		ans++;
		return ;
	}
	int nx = x+1, ny = y;
	if(x==W) nx = 1, ny++;
	if(vis[x][y]) return solve(s+1, nx, ny, a, b);
	if(a)
	{
		if(x!=W && !vis[nx][ny])
		{
			vis[x][y] = vis[nx][ny] = true;
			solve(s+1, nx, ny, a-1, b);
			vis[x][y] = vis[nx][ny] = false;
		} 
		if(y<H)
		{
			vis[x][y] = vis[x][y+1] = true;
			solve(s+1, nx, ny, a-1, b);
			vis[x][y] = vis[x][y+1] = false;
		} 
	}
	if(b)
	{
		vis[x][y] = true;
		solve(s+1, nx, ny, a, b-1);
		vis[x][y] = false;
	} 
}
int main()
{
	//freopen("/Users/zhangkanqi/Desktop/11.txt", "r", stdin);
	cin >> H >> W >> A >> B;
	solve(0, 1, 1, A, B);
	cout << ans << endl;
	return 0;
}
