#include <stdio.h>
#include <string.h>

int main()
{
	char A[101], B[101];
	char encrypt[] = "0123456789JQK";

	scanf("%s %s", A, B);
	int lenA = strlen(A);
	int lenB = strlen(B);
	int maxlen = lenA > lenB ? lenA : lenB;
	int a, b;

	for (int i = 0; i < maxlen; i++) {
		a = lenA + i - maxlen < 0 ? 0 : A[lenA + i - maxlen] - '0';
		b = lenB + i - maxlen < 0 ? 0 : B[lenB + i - maxlen] - '0';

		if ((maxlen - i) % 2)
			putchar(encrypt[(a + b) % 13]);
		else
			putchar('0' + (b - a < 0 ? b - a + 10 : b - a));
	}

	return 0;
}