#include <bits/stdc++.h>

#define ll long long
#define ld  double
using namespace std;

// #define int ll

const int N = 2e5 + 5, mod = 998244353;

ld dp[105], winningProb, losingProb;

int dwinning, dlosing;
int vis[105];

ld solve(int prizeProb) {
    if (prizeProb == 100) {
        return 1 / winningProb;
    }
    if (vis[prizeProb] == 1) return dp[prizeProb];
    vis[prizeProb] = 1;

    ld op1, op2, op3;
    // winning
    {
        op1 = winningProb * prizeProb / 100.0l;
        op2 = winningProb * (100.0l - prizeProb) / 100.0l * (1 + solve(min(100, prizeProb + dwinning)));
    }

    // losing
    {
        op3 = losingProb * (1 + solve(min(100, prizeProb + dlosing)));
    }

    return dp[prizeProb] = op1 + op2 + op3;
}



int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    ld g;
    cin >> dlosing >> dwinning >> g >> losingProb;

    winningProb = (100.0l - losingProb) / 100.0l;
    losingProb /= 100.0l;

   ld daysToWin = solve(0);
   cout << fixed << setprecision(10) << daysToWin * (100.0l / g);


    return 0;
}