#include <iostream>

using namespace std;

const long long MOD = 998244353;

int main(){
  long long h,w,k;cin>>h>>w>>k;
  long long ans = 0;
  for(int i = 0; k > i; i++){
    long long x,y,s;cin>>x>>y>>s;
    long long area = 0;
    if(x <= y)area += x*(x+1)/2;
    else area += x*(x+1)/2-(x-y)*(x-y+1)/2;
    if(y+x <= w+1)area += x*(x+1)/2;
    else area += x*(x+1)/2-(y+x-(w+1))*(y+x-(w+1)+1)/2;
    area %= MOD;
    area = (area+MOD-x)%MOD;
    ans = (ans+(area*s)%MOD)%MOD;
  }
  cout << ans << endl;
}