#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(){
    char s[101];
    int seen[256]={0};
    int i;
    fgets(s,sizeof(s),stdin);
    s[strcspn(s,"\n")]='\0';
    for(i=0;s[i];i++){
        if(!isalnum(s[i])&& !isspace(s[i])){
            printf("Invalid input\n");
            return 0;
        }
    }
    for (i=0;s[i];i++){
        char c=s[i];
        if(isalpha(c)){
            char lower=tolower(c);
        }
        if(!seen[(unsigned char)lower]){
            putchar(c);
            seen[(unsigned char)lower]=1;
        }
    }
    printf("\n");
    return 0;
}