#include <stdio.h>

int operation1(int *x, int *y, int *i);
int operation2(int *x, int *y, int *i);

int main(void){
    int X, Y, i = 0;
    scanf("%d%d", &X, &Y);
    if(X == Y){
        i = 0;
    }
    else if(X == 0){
        operation1(&X,&Y,&i);
        operation2(&X,&Y,&i);
    }
    else if(Y == 0){
        operation2(&X,&Y,&i);
    }
    else if(X == -Y){
        operation2(&X,&Y,&i);
        operation1(&X,&Y,&i);
        operation2(&X,&Y,&i);
    }
    else{
        i = -1;
    }
    printf("%d\n", i);
    return 0;
}

// X' = Y, Y' = X
int operation1(int *x, int *y, int *i){
    int t;
    t = *x;
    *x = *y;
    *y = t;
    *i += 1;
    return 0;
}

// X' = X + Y, Y' = X - Y
int operation2(int *x, int *y, int *i){
    int t;
    t = *x;
    *x += *y;
    *y = t - *y;
    *i += 1;
    return 0;
}