#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(){
    char s[101];
    int count[256]={0};
    int valid=1;
    fgets(s, sizeof(s),stdin);
    for(i=0;s[i]!='\0';i++){
        if(!(isalnums(s[i])
        ||isspace(s[i])||s[i]=='\n')){
            valid=0;
            break;
        }
    }
            if(!valid){
            printf("Invalid input");
            return 0;
        }
    for(i=0;s[i]!='\0';i++){
        if(!s[i]]!='\n'){
            result[j++]=s[i];
            count[(unsigned char)s[i]]=1;
        }
        for(int i=0;s[i]!='\0';i++)
        if(s[i]!='\n'&& count[(unsigned char)s[i]]==1)
    printf("%c",s[i]);
    }
    return 0;
}