#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main()
{
    char str[200];
    fgets(str,sizeof(str),stdin);
    int seen[256] = {0};
    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;
}