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