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