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

int main() {
    char s[101];
    
    fgets(s, sizeof(s),stdin);
    s strcspn(s,"\n")= '\0';
    
    for (int i = 0; s[i] != '\0'; i++) {
        if (!(isalnum(s[i]) || s[i] == ' ')) {
            printf("Invalid input");
            return 0;
        }
    }
    
    int seen[256] = {0};
    char result[101];
    int idx = 0;
    
    for (int i = 0; s[i] != '\0'; i++) {
        unsigned char c = s[i];
        if (!seen[c]) {
            result[idx++] = c;
            seen[c] = 1;
        }
    }
      result [idx] = '\0';
    
    
    printf("%s", result) ;
    
    
}