#include <stdio.h>
#define MOD 998244353

int a,b;
long long int func(int s, int t)
{
	long long int val1 = 0, val2 = 0, val3 = 0;
	val1 = (long long int)s*s;
	int L = t - (s-1), R = t + (s-1);
	if(L<1)
	{
		long long int v = 1-L;
		val2 = v*(v+1)/2;
	}
	if(R>b)
	{
		long long int v = R-b;
		val3 = v*(v+1)/2;
	}
	long long int ans = (val1 + MOD - val2 + MOD - val3)%MOD;
	return ans;
}

int main()
{
	int c;
	scanf("%d%d%d",&a,&b,&c);
	long long int ans = 0;
	for(int i=1;i<=c;i++)
	{
		int d,e,f;
		scanf("%d%d%d",&d,&e,&f);
		ans += (func(d,e)*f)%MOD, ans %= MOD;
	}
	printf("%lld",ans);
}