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

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

    for (int i = 0; s[i] != '\0'; i++) {
        if (!seen[(unsigned char)s[i]]) {
            result[j++] = s[i];
            seen[(unsigned char)s[i]] = 1;
        }
    }
    result[j] = '\0';

    printf("%s\n", result);

    return 0;
}