#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(){
    char s[105];
    int seen[256]={0};
    int i,j=0;
    fgets(s,sizeof(s), stdin);
    s[strcspn(s,"\n")]='\0';
    for(i=0;s[i]!='\0';i++){
        if(!(isalnum(s[i])||s[i]=='')){
            printf("Invalid input");
            return 0;
        }
    }
    for(i=0;s[i]!='\0';i++){
        unsigned char ch = s[i];
        unsigned char lower = tolower(ch);
        if(!seen[lower]){
            s[j++] = ch;
            seen[lower] = 1;
        }
    }
    s[j] = '\0';
    printf("%s",s);
    return 0;
}