#define N 1000

void kadai211() {
   double cnt = 0.0;
   for (int i = 0; i < N; i++) {
      double x = (double)rand() / RAND_MAX;
      double y = (double)rand() / RAND_MAX;
      if ((x * x + y * y) <= 1) cnt += 1.0;
   }
   cout << "pi: " << cnt / N * 4.0 << endl;
}