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