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

int main() {
 char s[101],result[101];
 int i,j = 0, seen[256] ={0};
 fgets(s, sizeof(s), stdin);
 s[strcspn(s, "\n")] = '\0';
 
 for (i = 0; s[i]; i++) {
     if(!(isalnum(s[i])|| s[i] == ' ')) {
         printf("Invalid input\n");
         return 0;
     }
 }
 
 for(i = 0; s[i]; i++) {
     unsigned char c = s[i];
     unsigned char lower = tolower(c);
     if(!seen[lower]) {
         result[j++] = c;
         seen[lower] = i;
     }
 }
 result[j] = '\0';
 printf("%s\n",result);
 return 0;
 
}