#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(){
    char s[101];
    if(fgets(s, sizeof(s),stdin)==NULL){
        printf("Invalid Input");
        return 0;
    }
    s[strcspn(s,"\n")]='\0';
    for(int i=0;s[i]!='\0';i++){
        if(!isalnum(s[i])&&s[i]!=' '){
            printf("Invalid Input");
            return 0;
        }
    }
    int seen[256]={0};
    for(int i=0;s[i]!='\0';i++){
        char ch=s[i];
        if(ch=='')
        continue;
        char lower=tolower(ch);
        if(!seen[(unsigned char)lower]){
            printf("%c",ch);
        }
    }
    return 0;
}