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