#include <stdio.h>
 int main(){
     char s1[101];
     char s2[101];
     scanf("%s",&s1);
     scanf("%s",&s2);
     for (int i=0;s1[i]!='\O'){
         if(!isalpha(s1[i])){
             printf("Invalid input");
             return 0;
         }
     }
      for (int i=0;s2[i]!='\O'){
         if(!isalpha(s2[i])){
             printf("Invalid input");
             return 0;
         }
     }
     strcat(s1,s2);
     printf("%s",s1);
     return 0;
 }










































    
    
    
    
    
    
    
    
    
 }