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

int main () {
	char pattern[100005], text[100005];
	while (scanf("%s %s", pattern, text) != EOF) {
		char *p = strstr(text, pattern);
		if (p == NULL) {
			printf("-1");
			continue;
		}
		
		int len1 = strlen(p);
		int len2 = strlen(pattern);
		for (int i = 0; i < len1 - len2; i++) {
			p[i] = p[i + len2];
		}
		p[len1 - len2] = '\0';
		
		printf("%s\n", text);
	}
	return 0;
}