#include <stdio.h>

int main(void){
    int x1, y1, x2, y2;
    scanf("%d %d %d %d", &x1, &y1, &x2, &y2);
    if(x1<0) x1 *= -1;
    if(y1<0) y1 *= -1;
    if(x1>=y1){
        printf("%d\n", x1);
    }else{
        printf("%d\n", y1);
    }
    return 0;
}