#include <stdio.h>
#include <string.h>
#include <ctype.h>
int isValid(char str[])
{
    for (int i = 0; str[i]; i++)
    {
        if (!(isalnum(str[i]) || str[i] == ' '))
        {
            return 0;
    }
    return 1;
}
void removeDuplicates(char str[])
{
    int seen[256] = {0};
    for (int i = 0; str[i]; i++)
    {
        char ch = str[i];
        char lowerCh = tolower(ch);
        if (!seen[(unsigned char)lowerCh])
        {
            printf("%c", ch);
            seen[(unsigned char)lowerCh] = 1;
        }
    }
}
int main()
{
    char str[101];
    fgets(str, sizeof(str), stdin);
    str[strcspn(str, "\n")] = 0; 
    if (!isValid(str))
    {
        printf("Invalid input\n");
        return 0;
    }
    removeDuplicates(str);
    return 0;
}
}