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





char lower(const char c) {
	if ('A' <= c && c <= 'Z') { return c + 32; }
	else { return c; }
}


int distance(char s1[], char s2[]) {
	int dist = 0;
	int i = 0;
	char c1, c2;
	do {
		c1 = s1[i];
		c2 = s2[i];
		dist += abs(lower(c2) - lower(c1));
		++i;
	} while (c1 != '\0' && c2 != '\0');
	if (c1 == c2) { return dist; }
	else { return (-1); }
}


int main() {
	char s1[256];
	char s2[256];
	scanf("%s", s1);
	scanf("%s", s2);
	printf("\ndistance: %d\n\n", distance(s1, s2));
}