#include<stdio.h>
#include<ctype.h>
#include<string.h>
int main()
{
    char str[101], result[101];
    int i,j =0;
    fgets(str, sizeof(str), stdin);
    str[strcspn(str, "\n")] = '\0';
    int len = strlen(str);
    for(i = 0; i < len; i++)
    {
        if(!(isalpha(str[i]) || isdigit(str[i]) || str[i] == ''))
        {
            printf("Invalid input");
            return 0;
        }
    }
    for (i = 0; i < len; i++)
    {
        int found = 0;
        for (int k = 0; k < j; k++)
        {
            if (result[k] == str[i])
            {
                found = 1;
                break;
            }
        }
        if (!found)
        {
            result[j++] = str[i];
        }
    }
    result[j] = '\0';
    printf("%s", result);
    return 0;
}