#include <stdio.h>
#include <stdlib.h>

int main(void) {
	char x[32], y[32];
	scanf("%s %s", &x, &y);
	long a = strtol(x, NULL, 2);
	long b = strtol(y, NULL, 2);
	long ans = a ^ b;
	printf("%ld\n", ans);
	
	return 0;
}