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// mrozik[@]gmail

#include <cstdio>
#include <algorithm>
using namespace std;

pair<int, int> T[2000000];

int main() {
  int n, m; scanf("%d%d", &n, &m);

  for (int i = 0 ; i < m ; i++) {
    int l, r, k; scanf("%d%d%d", &l, &r, &k);
    T[2*i] = make_pair(l, k);
    T[2*i + 1] = make_pair(r+1, -k);
  }

  sort(T, T + 2*m);

  int result = 0;

  int f[4] {};
  int lastP = 1;
  for (int ix = 0; ix < 2*m; ix++) {
    int p = T[ix].first;
    if (f[1] && f[2] && not f[3]) {
      result += p - lastP;
    }
    if (T[ix].second > 0) {
      f[T[ix].second]++;
    }
    else {
      f[-T[ix].second]--;
    }
    lastP = p;
  }

  printf("%d\n", result);

  return 0;
}