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#include <bits/stdc++.h>
#define REP(i,n) for(int _n=(n), i=0;i<_n;++i)

void init_io() {
  std::cin.tie(nullptr);
  std::ios::sync_with_stdio(false);
}

const int max_coord = 1000000;

class Deliveries {
public:
  Deliveries();
  int num_canceled() const;
private:
  std::vector<std::array<int,2>> planes;
};

Deliveries::Deliveries():
  planes(2*max_coord+1)
{
  int n;
  std::cin >> n;
  REP(i, n) {
    int r,w,t;
    std::cin >> r >> w >> t;
    --r;
    planes[t - w + max_coord][r] += 1;
  }
}

int Deliveries::num_canceled() const {
  int canceled = 0;
  for (const auto &plane : planes) {
    canceled += std::min(plane[0], plane[1]);
  }
  return canceled;
}

int main() {
  init_io();
  Deliveries deliveries;
  std::cout << deliveries.num_canceled() << "\n";
}