#include<stdio.h>
#include<string.h>
#include<ctype.h>

int main()
{
    char str[200];
    fgets(str,sizeof(str),stdin);
    int seen[256]={0};
    characters
    char result[200];
    int k=0;
    for(int i=0; str[i] !='\0';i++)
    {
        char c=str[i];
        if(!(isalnum(c) || isspace(c)))
        {
            printf("invalid input");
            return 0;
        }
        if(c=='')
        continue;
        if(!seen[(unsigned char)c])
        {
            result[k++]=c;
            seen[(unsigned char)c]=1;
        }
    }
    result[k]='\0';
    printf("%s",result);
    
    return 0;
}