#include <stdio.h>
#include <string.h>
int main() 
{
    char s[101],result[101];
    int count[256] = {0};
    
    int i,j = 0;
    fgets(s, sizeof(s), stdin);
    int len=strlen(s);
    if(len>0&&s[len -1]=='\n')
  {
      s[len -1]='\0';
  }
  for(i=0;s[i] !='\0';i++)
  {
      char ch = s[i];
      if((char>='A' && ch <='Z')||
         (char>='a' && ch <='Z')||
         (char>='0' && ch <='9')||
         ch =='')
  }
  else
  {
      printf("Invalid input\n");
      return 0;

  }
}
for(i=0;s[i] !='\0'; i++)
{
    if (count[(unsigned char)s[i]]==1)
    {
        result[j++]=s[i];
    }
    
    
    }
    result[j]='\0';
    printf("%s\n",result);
    
    return 0;
}