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

int isValid(vhar str[]){
    for (int i = 0; str[i] != '\0'; i++{
        if (!isalpha(str[i])){
            return 0;
        }
        
    }
    return 1;
}
int main(){
    char s1[101],s2[101];
    
    scanf("%s", s1);
    scanf("%s", s2);
    
    if (isValid(s1) && isValid(s2)){
        printf("%s%s", s1,s2);
    }else{
        printf("Invalid input");
    }
    retuen 0;
}