#include <bits/stdc++.h>
using namespace std;

const int N = 15, inf = 1e8;

double f[N][N][N][N][5][5];
int A, B, C, D;
bool v[N][N][N][N][5][5];

void add(int x, int y, int &a, int &b, int &c, int &d) {
    a += (x == 0) + (y == 0);
    b += (x == 1) + (y == 1);
    c += (x == 2) + (y == 2);
    d += (x == 3) + (y == 3);
}

double dfs(int a, int b, int c, int d, int x, int y) {
    if(v[a][b][c][d][x][y]) return f[a][b][c][d][x][y];
    v[a][b][c][d][x][y] = 1;
    double &ans = f[a][b][c][d][x][y] = 0;
    int na = a, nb = b, nc = c, nd = d;
    add(x, y, na, nb, nc, nd);
    if (na >= A && nb >= B && nc >= C && nd >= D) return 0;
	int w = 54 - na - nb - nc - nd;
	if (w <= 0) return ans = inf;
	if (a < 13) ans += dfs(a + 1, b, c, d, x, y) * (13 - a) / w;
	if (b < 13) ans += dfs(a, b + 1, c, d, x, y) * (13 - b) / w;
	if (c < 13) ans += dfs(a, b, c + 1, d, x, y) * (13 - c) / w;
	if (d < 13) ans += dfs(a, b, c, d + 1, x, y) * (13 - d) / w;
    double x_val = inf, y_val = inf;
    for(int i = 0; i < 4; i ++ ) {
        if(x == 4) x_val = min(x_val, dfs(a, b, c, d, i, y) / w);
        if(y == 4) y_val = min(y_val, dfs(a, b, c, d, x, i) / w);
    }
    if(x == 4) ans += x_val;
    if(y == 4) ans += y_val;
    return ++ ans;
}

int main() {
    cin >> A >> B >> C >> D;
    double ans = dfs(0, 0, 0, 0, 4, 4);
    if(ans >= inf) puts("-1.000");
    else printf("%.3lf", ans);
    return 0;
}

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