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

int isahabettic(char str[]){
    for (int i = 0; str [i] != '0'; i++){
        if (!isalpha(str [i])) // check if character is not alphabetic
        return 0;
    }
    return 1;
}
int main(){
    char s1[101], s2[101];
    scanf("%s", s1);
    scanf("%s", s2);
    
    if (isAlphabetic(s1) && isAlphabetic(s2)){
        printf("%s%s", s1, s2);
    }else{
        printf("Invalid input");
    }
}