#include<stdio.h>
#include<ctype.h>
#include<string.h>

int main(){
    char s[105];
    fgets(s, sizeof(s), stdin);
    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[250]={0};
    char result[105];
    int idx=0;
    for(int i=0; s[i]!='\0';i++){
        unsigned char c=s[i];
        if(!seen[c]){
            result[idx++]=c;
            seen[c] =1
    }
    }
    result[idx] = '\0';
    printf("%s", result);
    
    return 0;
}