// editor2
#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(){
    char s[101];
    int seen[256]={0};
    char resuit[101];
    intj=0;
    fgats(s,sizeof(s),stdin);
    s[strcspu(s,"\n")]='\0';
    for (int i=0;s[i]!='\0';++){
        if(!(isalnum(s[i])|| s[i]=='')){
            printf(" Invalid input");
            return 0;
        }
    }
    for(inti=0;s[i]!='\0';i++){
        if(!seen[(unsigned char)s[i]]){
            seen[(unsigned char)s[i]]=1;
            result[j++]=s[i];
        }
    }
    result[j]='\0';
    printf("%s",result);
    return 0;
}