#include <stdio.h>
#include <string.h>
#include <ctype.h>

int main() {
    char s[1005];
    int seen[256] = {0};
    char result[1005];
    int k = 0;

    if (!fgets(s, sizeof(s), stdin)) return 0;
    for (int i = 0; s[i] != '\0'; i++) {
        if (s[i] == '\n') continue;
        if (!(isalpha(s[i]) || isdigit(s[i]) || s[i] == ' ')) {
            printf("Invalid Input\n");
            return 0;
        }
    }
    for (int i = 0; s[i] != '\0'; i++) {
        char c = s[i];
        if (c == '\n' || c == ' ') continue;

        char lower = tolower(c);
        if (!seen[(unsigned char)lower]) {
            result[k++] = c;   
    }

    result[k] = '\0';
    printf("%s\n", result);
    return 0;
}