#include<bits/stdc++.h>
using namespace std;
int d[]={0,31,29,31,30,31,30,31,31,30,31,30,31};
int main(){
    int M,D,cnt;
    cin>>M>>D;
    cnt=D;
    for(int i=0;i<M;i++)cnt+=d[i];
    if(cnt/2%2)cout<<-1<<endl;
    else cout<<M+D<<endl;
}