#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(){
     char s[101];
     char result[101];
     int freq[256]={0};
     int k=0;
     int is_valid=0;
     fgets(s,sizeof(s),stdin);
     s[strcspn(s,"/n")] = 0;
     for(int i=0;i<strlen(s);i++){
         char ch = s[i];
         if (!isalnum(ch)&&ch!=''){
             is_valid=1;
             break;
         }
         if (freq[(unsigned char)ch]==0){
          result[k++]=ch;
          freq[(unsigned char)ch]=1;
         }
     }
     if(is_valid){
         printf("Invalid input");
     }else{
         printf("%s/n",result);
     }
     return 0;
}