#include<stdio.h>
#include<string.h>
int main(){
char s1[];
char s2[];
scanf("%s%s",&s1,&s2);
if(a<=s1<=z||A<=s1<=Z){
    printf("%s",strcat(s1,s2));
}
else if(a<=s2<=z||A<=s2<=Z){
    printf("%s",strcat(s1,s2));
}
else{
    printf("Invalid input");
}
}