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

int is_digit(char c) { return c >= '0' && c <= '9'; }
int is_letter(char c) {
  return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_';
}

char *KEYWORDS[] = {"if", "else", "while", "int", "return"};
int is_keyword(char *s) {
  for (int i = 0; i < 5; i++) {
    if (strcmp(s, KEYWORDS[i]) == 0) return 1;
  }
  return 0;
}

int main() {
  string src;
  printf("Enter source: ");
  scanf("%s", &src);
  int i = 0;
  while (src[i] != 0) {
    if (is_letter(src[i])) {
      string lex;
      while (is_letter(src[i]) || is_digit(src[i])) { lex += src[i]; i++; }
      if (is_keyword(lex)) printf("KW     %s\n", lex);
      else printf("ID     %s\n", lex);
    } else if (is_digit(src[i])) {
      string lex;
      while (is_digit(src[i])) { lex += src[i]; i++; }
      printf("NUM    %s\n", lex);
    } else if (src[i] == '+' || src[i] == '-' || src[i] == '*' || src[i] == '/' || src[i] == '=' || src[i] == '<' || src[i] == '>') {
      printf("OP     %c\n", src[i]);
      i++;
    } else if (src[i] == '(' || src[i] == ')' || src[i] == '{' || src[i] == '}' || src[i] == ';' || src[i] == ',') {
      printf("SYM    %c\n", src[i]);
      i++;
    } else {
      printf("ERROR  illegal char '%c' at %d\n", src[i], i);
      i++;
    }
  }
  return 0;
}