#include <stdio.h>
#include <ctype.h>
#include <string.h>
int main() {
    char s[101],result[101];
    int used[256] = {0},j = 0;
    fgets(s,sizeof(s), stdin);
    for(int i = 0; s[i] !='\0'; i++) {
        if (!(isalnum(s[i]) || s[i] == ' ')) {
            printf("Invalid input");
            return 0;
        }
    }
    for (int i = 0; s[i] != '\0'; i++) {
        unsigned char ch = s[i];
        if(!used[ch] && ch != '\n') {
            used[ch] = 1;
            result[j++] ch;
        }
    }
    result[j] = '\0';
    printf("%s",result);
    return 0;
      
    
}