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

int main() {
    char s[101], result[101];
    int idx = 0;

    // Read input string
    gets(s);  // simple input (note: unsafe in real programs, but ok for beginners)

    for(int i = 0; s[i] != '\0'; i++) {
        char ch = s[i];

        // Check if character is valid (letter, number, or space)
        if(!((ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9') || ch == ' ')) {
            printf("Invalid input\n");
            return 0;
        }

        // Check if character already exists in result
        int duplicate = 0;
        for(int j = 0; j < idx; j++) {
            if(result[j] == ch) {
                duplicate = 1;
                break;
            }
        }

        // Add to result if not duplicate and not space
        if(!duplicate && ch != ' ') {
            result[idx++] = ch;
        }
    }

    result[idx] = '\0'; // null terminate

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

    return 0;
}