#include <stdio.h>
#include <string.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[101],s2[101];
    scanf ("%100s",s1);
    scanf ("%100s",s2);
if (!isAlphabetic(s1)||(!isAplhabetic(s2)){
    printf ("invalid input");
    return 0;
}
char(username[202]);
strcpy(username,s1);
strcat(username,s2 );
printf ("%s",username );
return 0;
}