#include <stdio.h>
#include <stdlib.h>
/* Original practice program. MIT. Inputs are intentionally small. */
int reward(int coins) {
  if (coins < 0 || coins > 100) return -1;
  if (coins >= 10) return coins * 3 + 5;
  return coins * 3;
}
int main(int argc, char **argv) {
  if(argc != 2) return 2;
  char *end; long n = strtol(argv[1], &end, 10);
  if(end == argv[1] || *end || n < -1 || n > 101) return 2;
  printf("reward=%d\n", reward((int)n)); return 0;
}