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

int main() {
  char s[101], seen[256] = {0};
  scanf("%[^\n]", s);
  
  for (int i = 0; s[i]; i++)
  if (!isalnum(s[i]) && s[i] != ' ')
  return printf("Invalid input\n"), 0;
  
  for (int i = 0; s[i]; i++) {
      char c = s[i];
      if (c == ' ')
      continue;
              if (!seen[(unsigned char)c]) {
                  putchar(c);
                  seen[(unsigned char)c] = 1;
              }
              }
  }
  printf("\n");
  return 0;
}