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

int main() {
    char s[101];
    int seen[256] = {0};
    char result[101];
    int i, j = 0;

    fgets(s, sizeof(s), stdin);

    for (i = 0; s[i] != '\0'; i++) {
        if(!(isalnum(s[i]) || isspace(s[i]) || s[i] == '\n')){
            printf("Invalid input");
            return 0;
        }
    }
    
    for(i=0; s[i] !='\O'; i++){
        char c = s[i];
        if(c == '\n') continue;
        char lower = tolower(c);
        if(!seen[(int)lower]) {
            seen[(int)lower] = 1;
            result[j++] = c;
        }
    }
    result[j] = '\0';
    
    printf("%s\n", result);
    return 0;
}