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