#include <stdio.h>
#include <ctype.h>
int isAlphabetic(char str[])
{
    int i = 0;
    while (str[i] != '\0') {
        if (!isalpha(str[i]))
        {
            return 0;
            }
            i++;
        }
    }
    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");
    }
    return 0;
    }