#include <bits/stdc++.h>

using namespace std;

#define fst(t) std::get<0>(t)
#define snd(t) std::get<1>(t)
#define thd(t) std::get<2>(t)
#define unless(p) if(!(p))
#define until(p) while(!(p))

using ll = long long;
using P = std::tuple<int,int>;

const int dx[8] = {-1, 1, 0, 0, -1, -1, 1, 1}, dy[8] = {0, 0, -1, 1, -1, 1, -1, 1};

int f(int a, int b){
    if(a % b >= (b + 1) / 2){
        return a / b + 1;
    }
    return a / b;
}

int main(){
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    int A, B;
    std::cin >> A >> B;

    int res = -1;
    for(int i=1;i<=600;++i){
        for(int a=0;a<=i;++a){
            int b = i - a;
            if(f(100 * a, i) == A && f(100 * b, i) == B){
                res = i;
                break;
            }
        }

        if(res != -1){
            break;
        }
    }

    std::cout << res << std::endl;
}