#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main()
{
    char s[105];
    fgets(s, sizeof(s), stdin);
    size_t len=strlen(s);
    if(len>0 && s[len-1]=='\n')
  {
    s[len-1]='\0';
    len--;
}
   for(int i=0; i<len; i++)
   {
       if(!(isalnum(s[i])||isspace(s[i])))
       {
           printf("Invalid Input ");
           return 0;
       }
   }
   int seen[256]={0};
   char result[105];
   int k=0;
   for (int i=0; i< len; i++)
   {
       if(!seen[(unsigned char)s[i]])
       {
           seen[(unsigned char)s[i]]=1;
           result[k++]=s[i];
       }
       result[k]='\0';
       printf("%s", result);
       return 0;