#include <stdio.h>
int main () {
    char s1[5],s2[6],*p1,*p,newch;
    p1 = s1;
    p2 = s2;
    gets(s1);
    gets(s2);
    while(*p1++ == *p2++){
        newch = *p1 + *p2;
        printf("%s",newch);
    }
    return 0;
}