#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(){
    char str[200],result[200];
    int i,j=0;
    fgets(str,sizeof(str),stdin);
    str[strcspn(str,"\n")]='\0';
    
    for (i=0; str[i]!='\0'; i++){
        if(!(isalnum(str[i]) || str[i]=='')){
            printf("Invalid");
            return 0;
        }
    }
    for (i=0; str[i]!='\0';i++){
        int found=0;
        for (int k=0; k<j; k++){
            if (result[k]==str[i]){
                found=1;
                break;
        }
    }
    if (!found){
        result[j++] = str[i];
        }
    }
    result[j] ='\0';
    printf("%s",result);
    return 0;
}