#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main()
{
   char str[101],result[101];
   int seen[256]={0};
   int k=0;
   if(!fgets(str,sizeof(str),stdin))
   {
       printf("Invalid input");
       return 0;
   }
   str[strcmp(str,"\n")]='\0';
   int n=strlen(str);
   if(n<1 || n>100)
   {
       printf("Inavlid input");
       return 0;
   }
   for(int i=0;i<n;i++)
   {
       char c=str[i];
       if(!(isalpha(c) || isdigit(c) || c==''))
       {
         printf("Invalid input");
         return 0;
       }
       if(!seen[unsigned char)c])
       {
           result[k++]=c;
           seen[(unsigned char)c]=1;
       }
   }
   result[k]='\0';
   printf("%s",result);
   return 0;
}