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#include <bits/stdc++.h>
using namespace std;

void Solve() {
  int n, m;
  cin >> n >> m;

  vector<vector<int>> sums(n + 1, vector<int>(3));
  for (int i = 0; i < m; ++i) {
    int l, r, b;
    cin >> l >> r >> b;
    --b;
    ++sums[l - 1][b];
    --sums[r][b];
  }

  int result = 0;
  int sum[3] = {0, 0, 0};
  for (int i = 0; i < n; ++i) {
    int cur_mask = 0;
    for (int j = 0; j < 3; ++j) {
      sum[j] += sums[i][j];
      if (sum[j] > 0)
        cur_mask |= 1 << j;
    }

    if (cur_mask == 3)
      ++result;
  }

  cout << result << '\n';
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  Solve();
}