#include <stdio.h>
#include <ctype.h>
#include <string.h>
int main(){
    char str[100],result[100];
    int k=0;
    fgets(str, sizeof(str),stdin);
    for(int i=0; str[i] && str[i] !='\n'; i++){
        char c = str[i];
        if(!(isalnum(c)||c =='')) {
            printf("Invalid input\n");
            return 0;
        }
        int found=0;
        for (int j=0; j<k; j++){
            if(result[j]==c){
                found=1;
                break;
            }
        }
        if(!found)result[k++]=c;
       }
       result[k]='\0';
       printf("%s\n",result);
       return 0;
}