#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define db double
#define pii pair<int,int>
#define pll pair<ll,ll>
#define ti3 tuple<int,int,int>
#define int128 __int128_t
#define pii128 pair<int128,int128>
const int inf = 1 << 30;
const ll linf = 1e18;
const ll mod = 998244353;
const db EPS = 1e-10;
const db pi = acos(-1);
template<class T> bool chmin(T& x, T y){
    if(x > y) {
        x = y;
        return true;
    } else return false;
}
template<class T> bool chmax(T& x, T y){
    if(x < y) {
        x = y;
        return true;
    } else return false;
}

// overload macro
#define CAT( A, B ) A ## B
#define SELECT( NAME, NUM ) CAT( NAME, NUM )

#define GET_COUNT( _1, _2, _3, _4, _5, _6 /* ad nauseam */, COUNT, ... ) COUNT
#define VA_SIZE( ... ) GET_COUNT( __VA_ARGS__, 6, 5, 4, 3, 2, 1 )

#define VA_SELECT( NAME, ... ) SELECT( NAME, VA_SIZE(__VA_ARGS__) )(__VA_ARGS__)

// rep(overload)
#define rep( ... ) VA_SELECT(rep, __VA_ARGS__)
#define rep2(i, n) for (decay_t<decltype(n)> i = 0; i < n; i++)
#define rep3(i, a, b) for (decay_t<decltype(a)> i = a; i < b; i++)
#define rep4(i, a, b, c) for (decay_t<decltype(a)> i = a; i < b; i += c)

// rrep(overload)
#define rrep( ... ) VA_SELECT(rrep, __VA_ARGS__)
#define rrep2(i, n) for (decay_t<decltype(n)> i = n - 1; i >= 0; i--)
#define rrep3(i, a, b) for (decay_t<decltype(a)> i = b - 1; i >= a; i--)
#define rrep4(i, a, b, c) for (decay_t<decltype(a)> i = b - 1; i >= a; i -= c)

// for_earh
#define fore(e, v) for (auto&& e : v)

// vector
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()

template<class T, T(* op)(T, T)>
struct segment_tree{
    int N;
    T e;
    vector<T> node;

    segment_tree(int n, T e) : e(e) {
        N = 1;
        while(N < n) N *= 2;
        node.resize(N * 2 - 1, e);
    }

    void update(int i, T x){
        i += N - 1;
        node[i] = x;
        while(i > 0){
            i = (i - 1) / 2;
            node[i] = op(node[i * 2 + 1], node[i * 2 + 2]);
        }
    }

    T get_val(int a, int b, int k = 0, int l = 0, int r = -1){
        if(r == -1) r = N;
        if(b <= l || r <= a) return e;
        if(a <= l && r <= b) return node[k];

        T vl = get_val(a, b, k * 2 + 1, l, (l + r) / 2);
        T vr = get_val(a, b, k * 2 + 2, (l + r) / 2, r);
        return op(vl, vr);
    }
};

template<long long mod>
struct modint{
    long long num;

    constexpr modint(long long x = 0) : num((x + mod) % mod) {}

    constexpr modint &operator += (const modint& rhs){
        num = (num + rhs.num) % mod;
        return *this;
    }
    constexpr modint &operator -= (const modint& rhs){
        num  -= rhs.num;
        while(num < 0) num += mod;
        num %= mod;
        return *this;
    }
    constexpr modint &operator *= (const modint& rhs){
        num = num * rhs.num % mod;
        return *this;
    }
    constexpr modint &operator /= (modint rhs){
        int exp = mod - 2;
        while(exp > 0){
            if(exp % 2){
                *this *= rhs;
            }
            rhs *= rhs;
            exp /= 2;
        }
        return *this;
    }

    constexpr modint operator ++ (){
        num = (num + 1) % mod;
        return *this;
    }
    constexpr modint operator ++ (int n){
        (void)n;
        modint tmp = *this;
        ++(*this);
        return tmp;
    }
    constexpr modint operator -- (){
        num = (num + mod - 1) % mod;
        return *this;
    }
    constexpr modint operator -- (int n){
        (void)n;
        const modint tmp = *this;
        --(*this);
        return tmp;
    }

    void modpow(ll y){
        modint tmp = (*this);
        (*this) = 1;
        while(y > 0){
            if(y % 2){
                (*this) *= tmp;
            }
            tmp *= tmp;
            y /= 2;
        }
    }

    constexpr modint operator + (const modint& rhs) const {
        return modint(*this) += rhs;
    }
    constexpr modint operator - (const modint& rhs) const {
        return modint(*this) -= rhs;
    }
    constexpr modint operator * (const modint& rhs) const {
        return modint(*this) *= rhs;
    }
    constexpr modint operator / (const modint& rhs) const {
        return modint(*this) /= rhs;
    }

    
    friend ostream &operator << (ostream& lhs, const modint& rhs){
        return lhs << rhs.num;
    }

    friend istream &operator >> (istream& lhs, modint& rhs){
        lhs >> rhs.num;
        return lhs;
    }
};

#define mint modint<mod>

mint modpow(mint x, ll y){
    if(y == 0) return 1;
    mint e = modpow(x, y / 2);
    e = e * e;
    return e * (y % 2 == 0 ? 1 : x);
}

mint op(mint a, mint b) {
    return a + b;
}

int H, W, K;
vector<pii> q[400010];
vector<int> p[400010];
int main() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(20);
    cin >> H >> W >> K;
    rep (i, K) {
        int x, y, v;
        cin >> x >> y >> v;
        int rx = x + y, ry = x - y + W;
        q[rx].emplace_back(ry, v);
    }

    rep (i, 1, H + 1) rep (j, 1, W + 1) {
        int rx = i + j, ry = i - j + W;
        p[rx].push_back(ry);
    }

    mint ans = 0;
    int N = H + W + 10;
    segment_tree<mint, op> st(N, (mint)0);
    rrep (i, 2, H + W + 1) {
        for (auto& [ry, v] : q[i]) {
            st.update(ry, st.get_val(ry, ry + 1) + v);
        }
        fore (e, p[i]) ans += st.get_val(e, N);
    }

    cout << ans << "\n";
}