CUONTINGLETTERS

#include <stdio.h>

int main() {
  int n;
  scanf("%d", &n);
  if (n < 1) {
    printf("Pogresan unos");
    return 1;
  }

  FILE *open = fopen("input.txt", "r");
  if (open == NULL) {
    printf("Datoteka input.txt ne postoji");
    return 1;
  }
  FILE *upis = fopen("output.txt", "w");
  int c;
  while ((c = fgetc(open)) != EOF) {
    int slovo = c, brojac = 1, usao=1;
    for (c = fgetc(open); c != EOF && c == slovo; c = fgetc(open), brojac++, usao=1);

    if (brojac >= n) {
      int i;
      for (i = 0; i < brojac; i++) {
        fputc(slovo, upis);
      }
    }
    if (c == EOF)
      break;
    if (usao)
      fseek(open, -1, SEEK_CUR);
  }

  fclose(open);
  fclose(upis);
  return 0;
}