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