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