#include <stdio.h>

int main () {
  int h = 0;
  long long w = 0LL;
  int k = 0;
  long long x = 0LL;
  long long y = 0LL;
  long long v = 0LL;
  
  int res = 0;
  
  long long ans = 0LL;
  long long mod_num = 998244353LL;
  
  res = scanf("%d", &h);
  res = scanf("%lld", &w);
  res = scanf("%d", &k);
  for (int i = 0; i < k; i++) {
    long long cnt = 0LL;
    res = scanf("%lld", &x);
    res = scanf("%lld", &y);
    res = scanf("%lld", &v);
    cnt = (x*x)%mod_num;
    if (x-y > 0LL) {
      cnt -= (((x-y)*(x-y+1LL))/2LL)%mod_num;
      cnt += mod_num;
      cnt %= mod_num;
    }
    if (x-(w-y+1LL) > 0LL) {
      cnt -= (((x-(w-y+1LL))*(x-(w-y+1LL)+1LL))/2LL)%mod_num;
      cnt += mod_num;
      cnt %= mod_num;
    }
    ans += cnt*v;
    ans %= mod_num;
  }
  
  printf("%lld\n", ans%mod_num);
  return 0;
}