#include <iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<map>
#include<set>
#include<stack>
#include<queue>
#include<math.h>
using namespace std;
typedef long long ll;
#define int long long
#define double long double
typedef vector<int> VI;
typedef pair<int, int> pii;
typedef vector<pii> VP;
typedef vector<string> VS;
typedef priority_queue<int> PQ;
template<class T>bool chmax(T &a, const T &b) { if (a < b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b < a) { a = b; return 1; } return 0; }
#define fore(i,a) for(auto &i:a)
#define REP(i,n) for(int i=0;i<n;i++)
#define eREP(i,n) for(int i=0;i<=n;i++)
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define eFOR(i,a,b) for(int i=(a);i<=(b);++i)
#define SORT(c) sort((c).begin(),(c).end())
#define rSORT(c) sort((c).rbegin(),(c).rend())
#define LB(x,a) lower_bound((x).begin(),(x).end(),(a))
#define UB(x,a) upper_bound((x).begin(),(x).end(),(a))
#define PRINT(a) printf("%.15Lf\n",a);
#define YESNO(a) cout << (a ? "YES" : "NO") << endl
#define YesNo(a) cout << (a ? "Yes" : "No") << endl
#define yesno(a) cout << (a ? "yes" : "no") << endl
#define INF 1000000000
#define LLINF 9223372036854775807
#define mod 1000000007
#define eps 1e-12 
//priority_queue<int,vector<int>, greater<int> > q2;



signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	bool ok = 1;
	int A, B, C, X, Y;
	string S, T;

	int D;
	cin >> A >> B >> C >> D;

	int ans = -INF;
	
	eFOR(x, A, B) {
		eFOR(y, C, D) {
			chmax(ans, x - y);
		}
	}

	cout << ans << endl;
	return 0;
}


// D - increment of coins
#include <bits/stdc++.h>
using namespace std;

#define N 100
double dp[N][N][N];
bool vis[N][N][N];

double f(int g, int s, int b){ // g=gold, s=silver, b=bronze
	if(g==N || s==N || b==N) return 1;
	if(vis[g][s][b]) return dp[g][s][b] + 1;
	vis[g][s][b] = true;
	int t = g + s + b;
	dp[g][s][b] = f(g+1,s,b)*g/t + f(g,s+1,b)*s/t + f(g,s,b+1)*b/t;
	return dp[g][s][b] + 1;
}

int main(){
	int G, S, B; cin>>G>>S>>B;
	cout<<setprecision(9)<<fixed<< f(G, S, B) - 1 <<endl;
}
