#include <stdio.h>
#include <ctype.h>
int isalphabetic(char str[]){
    for(int i = 0; str[i] != '\0'; i++){
        if(!isalpha(str[i])){
            return 0;
        }
    }
    return 1;
}
int main(){
    char s1[100], s2[100];
    scanf("%d %d", s1,s2);
    if(isalphabetic(s1) && isalphabetic(s2)){
        printf("%s%s", s1,s2);
    }
    else{
        printf("Invalid input");
        return 0;
    }
    return 0;
}