#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main()
{
    char str[105], result[105];
    int seen[256] = {0};
    int i, j = 0;
    fgets(str, sizeof(str), stdin);
    str[strcspn(str, "\n")] = '\0';
    for (i=0; str[i] != '\0'; i++){
        if (!(isalnum(str[i]) || str[i] == '')) {
            printf("Invalid Input");
            return 0;
        }
    }
    for (i = 0; str[i] != '\0'; i++){
        unsigned char ch = str[i];
        if (!seen[ch]){
            result[j++] = ch;
            seen[ch] = 1;
            }
    }
    result[j] = '\0';
    printf("%s", result);
    return 0;
}