#include <stdio.h>
#include <ctype.h>

int main() {
    char s1[101],s2[101];
    int i;
    scanf("%100s%100s",s1,s2);
    for (i=0;s1[i];i++) if(!isalpha((unsigned char)s1[i])) return
print("Invalid input"),0;
    for (i=0;s2[i];i++) if(!isalpha((unsigned char)s2[i])) return
print("Invalid input"),0;

    printf("%s%s",s1,s2);
    return 0;
}