#include <stdio.h>
int main() {
    int x,y;
    scanf("%d %d",&x,&y);
    if(x==y) printf("0");
    else if(x==0) printf("2");
    else if(y==0) printf("1");
    else if(x+y==0) printf("3");
    else printf("-1");
    return 0;
}