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

#define REP(i, n) for (int i = 0; i < (int)n; i++)
#define ST first
#define ND second
#define MP make_pair
#define PB push_back

typedef vector<int> VI;
typedef pair<int, int> PII;
typedef vector<PII> VPII;
typedef set<int> SI;
typedef long long LL;

#ifdef DEBUG
const bool debug = true;
#else
const bool debug = false;
#endif

// #define MULTI_TASK true

const int INF = 1000 * 1000 * 1000;
const LL INFLL = 1e18;
const int MAKSN = 1000 * 1000 + 13;
const LL MOD = 123456789LL;
LL N, M, k, l, a, b, c, d, r;
vector<LL> v;

void zeruj() {
    v.clear();
}

void readIn() {
    cin >> N >> M;
}

void solve() {
    set<int> cols[3];

    for (int j = 0; j < 3; j++) {
        for (int i = 1; i <= N; i++) {
            cols[j].insert(i);
        }
    }

    for (int i = 0; i < M; i++) {
        cin >> l >> r >> k;
        k--;
        auto it = cols[k].lower_bound(l);
        vector<int> todel;
        while (it != cols[k].end() && (*it) <= r) {
            todel.push_back(*it);
            it++;
        }
        for (auto v : todel) {
            cols[k].erase(v);
        }
    }

    int res = 0;
    for (int i = 1; i <= N; i++) {
        int val = 0;
        for (int k = 0; k < 3; k++) {
            val |= (1 << k) * (cols[k].find(i) == cols[k].end());
        }
        if (val == 3)
            res++;
    }
    cout << res << "\n";
}

int main() {
    ios_base::sync_with_stdio(0);
#ifdef MULTI_TASK
    int test;
    cin >> test;
    while (test--) {
#endif
        zeruj();
        readIn();
        solve();
#ifdef MULTI_TASK
    }
#endif
    return 0;
}