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#include <bits/stdc++.h>

using namespace std;

const int N = 1000000 + 50;

int pref[N][3];
int n, m;

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    int l, r, k;
    cin >> l >> r >> k;
    k--;
    pref[l][k]++;
    pref[r + 1][k]--;
  }
  int ans = 0;
  for (int i = 1; i < n; i++) {
    int mask = 0;
    for (int j = 0; j < 3; j++) {
      pref[i][j] += pref[i - 1][j];
      mask |= (pref[i][j] > 0) << j;
    }
    ans += (mask == 3);
  }
  cout << ans;

  return 0;
}