#include<stdio.h>
#include<string.h>
#include<ctype.h>
int main(){
    char str[105];
    fgets(str, sizeof(str), stdin);
    size-t  len= strlen(str);
    if (len > 0 && str[len -1] =='\n')
    {
        str[len - 1] = '\0';
        len--;
    }
    for(int i =0 ;i < len; i++)
    {
    if(!(isalapha(str[i]) || isdigit (str[i]) || str[i] == ' '))
    {
        printf("invalid input\n");
        return 0;
    }
}
   int visited[205] ={0};
char result[105];
int idx = 0;
for (int i = 0; i < len; i++)
{
    unsingned char ch =str[i];
    if(ch == ' ')
    continue;
    if(!visited[ch])
    {
        result[idx++] = ch;
        visited[ch] =1;
    }
}
    
        result[idx] = ' \0';
        printf("%s\n", result);
        return 0;
}