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

template<class T>
bool chmax(T& a, const T& b) {
    if (a < b) { a = b; return true; }
    return false;
}
template<class T>
bool chmin(T& a, const T& b) {
    if (b < a) { a = b; return true; }
    return false;
}

// std::vector Declaration
template<typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }
template<typename T, typename... Ts>
auto make_v(size_t a, Ts... ts) {
    return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

// std::vector Declaration and Initialization
template<typename T>
vector<T> make_vector(size_t a, T x) { return vector<T>(a, x); }
template<typename T, typename U, typename... Ts>
auto make_vector(size_t a, U b, Ts... ts) {
    return vector<decltype(make_vector<T>(b,ts...))>(a, make_vector<T>(b, ts...));
}

// std::vector Input
template<typename T>
istream& operator>>(istream& is, vector<T>& v) {
    for (auto &e : v) is >> e;
    return is;
}

// std::vector Debug
template<typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    os << "[";
    bool a = 1;
    for (auto e : v) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "]";
    return os;
}

// std::array Debug
template<typename T, size_t n>
ostream& operator<<(ostream& os, const array<T, n>& v) {
    os << "[";
    bool a = 1;
    for (auto e : v) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "]";
    return os;
}

// std::deque Debug
template<typename T>
ostream& operator<<(ostream& os, const deque<T>& d) {
    os << "[";
    bool a = 1;
    for (auto e : d) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "]";
    return os;
}

// std::pair Debug
template<typename T, typename U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << "(" << p.first << " " << p.second << ")";
    return os;
}

// std::set Debug
template<typename T>
ostream& operator<<(ostream& os, const set<T>& st) {
    os << "{";
    bool a = 1;
    for (auto e : st) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "}";
    return os;
}

// std::multiset Debug
template<typename T>
ostream& operator<<(ostream& os, const multiset<T>& st) {
    os << "{";
    bool a = 1;
    for (auto e : st) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "}";
    return os;
}

// std::map Debug
template<typename T, typename U>
ostream& operator<<(ostream& os, const map<T, U>& mp) {
    os << "{";
    bool a = 1;
    for (auto e : mp) {
        os << (a ? "" : " ");
        os << e.first << ":" << e.second;
        a = 0;
    }
    os << "}";
    return os;
}

// std::tuple Debug
template<int N, class Tuple>
void out(ostream& os, const Tuple& t){}
template<int N, class Tuple, class H, class ...Ts>
void out(ostream& os, const Tuple& t) {
    if (N) os << " ";
    os << get<N>(t);
    out<N+1,Tuple,Ts...>(os, t);
}
template<class ...Ts>
ostream& operator<<(ostream& os, const tuple<Ts...>& t) {
    os << "(";
    out<0,tuple<Ts...>,Ts...>(os, t);
    os << ")";
    return os;
}

// Debug
#define DUMP(x) cerr<<#x<<" = "<<(x)<<endl

// Weighted edge
template<typename T>
struct edge {
    int src, to;
    T cost;

    edge() {}
    edge(int to, T cost) : src(-1), to(to), cost(cost) {}
    edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

    friend ostream& operator<<(ostream& os, const edge& e) {
        return os << "(" << e.src << "->" << e.to << ":" << e.cost << ")";
    }
};

using LL = int64_t;

#define fs first
#define sc second

const int64_t MOD = 1e9+7;

template<typename OM>
struct DualSegmentTree {
    int sz;
    vector<OM> lazy;
    const function<OM(OM,OM)> h;
    const OM oe;
    // h: 作用素をマージする関数
    // oe: 作用素の単位元

    DualSegmentTree(
            int n,
            const function<OM(OM,OM)>& h,
            const OM& oe
            ) : h(h), oe(oe) {
        sz = 1;
        while (sz < n) sz <<= 1;
        lazy.assign(2*sz, oe);
    }

    void set(int i, const OM& x) {
        lazy.at(i + sz) = x;
    }

    OM merge(const OM& a, const OM& b) {
        if (a == oe) return b;
        if (b == oe) return a;
        return h(a, b);
    }

    void propagate(int k, int len) {
        if (lazy[k] == oe) return;
        if (k < sz) {
            lazy[2*k  ] = merge(lazy[2*k  ], lazy[k]);
            lazy[2*k+1] = merge(lazy[2*k+1], lazy[k]);
            lazy[k] = oe;
        }
    }

    void _update(int a, int b, const OM& x, int k, int l, int r) {
        propagate(k, r - l);
        if (r <= a or b <= l) return;
        else if (a <= l and r <= b) {
            lazy[k] = merge(lazy[k], x);
            propagate(k, r - l);
        } else {
            _update(a, b, x, 2*k,   l, (l+r)/2);
            _update(a, b, x, 2*k+1, (l+r)/2, r);
        }
    }

    void update(int a, int b, const OM& x) {
        // update [a, b) with x.
        _update(a, b, x, 1, 0, sz);
    }

    OM _query(int i, int k, int l, int r) {
        if (l+1 == r) return lazy[l + sz];
        propagate(k, r - l);
        int m = (l+r)/2;
        if (i < m) return _query(i, 2*k,   l, m);
        else       return _query(i, 2*k+1, m, r);
    }

    OM operator[](int i) {
        // return f[a, b).
        return _query(i, 1, 0, sz);
    }
};

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    int n, k, t; cin >> n >> k >> t;
    using P = pair<int,int>;
    DualSegmentTree<P> segt(
            n,
            [](P a, P b){
                if (a.second == b.first) {
                    return make_pair(a.first,b.second);
                }
                return make_pair(0, 0);
            }, make_pair(-1, -1));

    for (int i = 0; i < n; ++i) {
        segt.set(i, make_pair(0, 1));
    }

    for (int i = 0; i < t; ++i) {
        int l, r, x; cin >> l >> r >> x;
        segt.update(l-1, r, make_pair(x, x+1));
    }

    int ans = 0;
    for (int i = 0; i < n; ++i) {
        if (segt[i].second == k+1) {
            ++ans;
        }
    }
    cout << ans << endl;


    return 0;
}



Measured memory_bytes: 7064