#include <stdio.h>

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