#include <stdio.h>
#include<math.h>

int main() {
    int x1,y1,x2,y2;
    scanf("%d %d\n%d %d",&x1,&y1,&x2,&y2);
    x1 = x1-x2;
    x1 = x1*x1;
    y1 = y1-y2;
    y1 = y1*y1;
    printf("%d",x1+y1);
    return 0;
}