// Created by Nikolay Budin
#ifdef LOCAL
# define _GLIBCXX_DEBUG
#else
# define cerr __get_ce
#endif
#include <bits/stdc++.h>
#define ff first
#define ss second
#define szof(x) ((int)x.size())
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef unsigned long long ull;
int const INF = (int)1e9 + 1e3;
ll const INFL = (ll)1e18 + 1e6;
#ifdef LOCAL
mt19937 tw(9450189);
#else
mt19937 tw(chrono::high_resolution_clock::now().time_since_epoch().count());
#endif
uniform_int_distribution<ll> ll_distr;
ll rnd(ll a, ll b) { return ll_distr(tw) % (b - a + 1) + a; }
const int MOD = 998244353;
struct cells_order {
bool operator()(pii p1, pii p2) {
return p1.ff - p1.ss < p2.ff - p2.ss || (p1.ff - p1.ss == p2.ff - p2.ss && p1.ff + p1.ss < p2.ff + p2.ss);
}
};
void solve() {
int h, w, n;
cin >> h >> w >> n;
int m = max(h, w);
vector<set<pii, cells_order>> intr_cells(2);
map<pii, int> inp;
for (int i = 0; i < n; ++i) {
int x, y, v;
cin >> x >> y >> v;
--y;
x = m - x;
inp[{x, y}] = v;
for (int dx = 0; dx <= 2; ++dx) {
for (int dy = -2; dy <= 0; ++dy) {
if (abs(dx) + abs(dy) <= 2) {
int nx = x + dx;
int ny = y + dy;
if (0 <= nx && nx < m && 0 <= ny && ny < m) {
intr_cells[(nx + ny) & 1].insert({nx, ny});
}
}
}
}
}
int ans = 0;
vector<pii> change;
for (int q = 0; q < 2; ++q) {
// cerr << "q: " << q << endl;
auto it = intr_cells[q].begin();
ll sum = 0;
map<int, int> arr;
int prev = -INF;
while (it != intr_cells[q].end()) {
int i = it->ff - it->ss;
// cerr << i << " " << prev << " " << sum << endl;
ans = (ans + (ll) (i - prev) / 2 * (sum % MOD)) % MOD;
int l = abs(i);
int r = m * 2 - 2 - abs(i);
if (i <= 0) {
sum += arr[l];
if (l != r) {
sum += arr[r];
}
} else if (i > 1) {
sum -= arr[l - 2];
sum -= arr[r + 2];
}
change.clear();
while (it != intr_cells[q].end() && it->ff - it->ss == i) {
int x, y;
tie(x, y) = *it;
if (inp.count({x, y})) {
//arr[x + y] = inp[{x, y}];
change.push_back({x + y, inp[{x, y}]});
} else {
int val1;
if (x == 0) {
val1 = 0;
} else if (inp.count({x - 1, y})) {
val1 = inp[{x - 1, y}];
} else {
val1 = max(arr[x + y], x + y - 2 >= 0 ? arr[x + y - 2] : 0);
}
int val2;
if (y == m - 1) {
val2 = 0;
} else if (inp.count({x, y + 1})) {
val2 = inp[{x, y + 1}];
} else {
val2 = max(arr[x + y], x + y + 2 < m * 2 ? arr[x + y + 2] : 0);
}
// arr[x + y] = min(val1, val2);
change.push_back({x + y, min(val1, val2)});
if (x + y < m - 2) {
intr_cells[q].insert({x + y + 2, 0});
} else if (x + y >= m + 1) {
intr_cells[q].insert({m - 1, x + y - (m - 1) - 2});
}
}
++it;
}
for (pii p : change) {
if (l <= p.ff && p.ff <= r) {
sum -= arr[p.ff];
}
arr[p.ff] = p.ss;
if (l <= p.ff && p.ff <= r) {
sum += arr[p.ff];
}
}
prev = i;
// cerr << sum << endl;
// for (int j = l; j <= r; j += 2) {
// cerr << arr[j] << " ";
// }
// cerr << endl;
}
// cerr << ((m & 1) == q ? m : m + 1) << " " << prev << " " << sum << endl;
ans = (ans + (ll) (((m & 1) == q ? m : m + 1) - prev) / 2 * (sum % MOD)) % MOD;
}
cout << (ans + MOD) % MOD << "\n";
}
int main() {
#ifdef LOCAL
auto start_time = clock();
cerr << setprecision(3) << fixed;
#endif
cout << setprecision(15) << fixed;
ios::sync_with_stdio(false);
cin.tie(nullptr);
int test_count = 1;
// cin >> test_count;
for (int test = 1; test <= test_count; ++test) {
solve();
}
#ifdef LOCAL
auto end_time = clock();
cerr << "Execution time: " << (end_time - start_time) * (int)1e3 / CLOCKS_PER_SEC << " ms\n";
#endif
}
