#include<stdio.h>
#include<string.h>
#include<ctype.h>
int isAlphabetic(char *str)
{
    while(*str)
    {
        if(isalpha(* str))
        {
            return 0;
        }
        str++;
    }
    return 1;
}
int main()
{
    char s1[101],s2[101];
    scanf("%s",s1);
    scanf("%s",s2);
    if(isAlphabetic(s1)||isAlphabetic(s2))
    {
        printf("Invalid input\n")
        return 0;
    }
    printf("%s%s\n",s1,s2);
    return 0;
}