#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
using namespace std;
int N, K;
int main(){
    cin >> N >> K;
    int d = (0.8+0.2*K)*10;
    if((N*500)%d == 0) cout << 50*N + (50 * N) / (0.8 + 0.2 * K) << endl;
    else cout << 50*N + floor((50 * N) / (0.8 + 0.2 * K)) << endl;
    return 0;
}