// editor1
#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main()
{
    char s[101];
    int seen[256]={0};
    int i;
    scanf("%[^\n]",s);
    for(i=0;s[i]!='\0';i++)
    {
        if(!isalnum(s[i])&&s[i]!=' '){
            printf("Invalid input\n");
            return 0;
        }
    }
    for(i=0;s[i]!='\0';i++){
        if(isalnum(s[i])&&!seen[(unsigned char)s(i)]){
            printf("%c",s[i]);
            seen[(unsigned char)s(i)]=1;
        }
    }
    printf("\n");
    retrun 0;
}