#include<stdio.h>
#include<ctype.h>
#include<string.h>
{
    char s1[100],s2[100];
    int i;
    if(scanf("%s%s",s1,s2)!=2)
    {
        printf("Invalid input");
        return 0;
    }
    for(i=0;s1[i]!=' ';i++)
    {
        if(!isalpha((unsigned char)s1[i]))
        {
            printf("Invalid input");
            return 0;
        }
    }
    for(i=0;s2[i]!=' ';i++)
    {
        if(!isalpha((unsigned char)s2[i])
        {
            printf("Invalid input");
            return 0;
        }
    }
    printf("%s%s",s1,s2);
    return 0;
}