#include"iostream"
#include"cstdio"
#include"cmath"
#include"cstring"
using namespace std;

#define read(x) scanf("%d",&x)

int n,m,t,k;
int a[4005][4005];
int l,r,v;
int dp[4005][4005];
int q[4005],loc[4005],head=0,tail=1;
int ans=0;

int main()
{
	read(n),read(m),read(k),read(t);
	//cout<<n<<" "<<m<<endl;
	for(int i=1;i<=k;i++)
	{
		read(l),read(r),read(v);
		a[l][r]=v;
	}
	for(int i=1;i<=m;i++) dp[1][i]=a[1][i];
	if(m<=t+1)
	{
		int ans=0;
		for(int i=1;i<=n;i++)
		{
			int now=0;
			for(int j=1;j<=m;j++) now=max(now,a[i][j]);
			ans+=now;
		}
		printf("%d\n",ans);
		return 0;
	}
	for(int i=2;i<=n;i++)
	{
		memset(q,0,sizeof(q)),memset(loc,0,sizeof(loc));
		head=0,tail=1;
		for(int j=1;j<=m;j++)
		{
			//cout<<i<<" "<<j<<endl;
			while(head>=tail&&q[head]<=dp[i-1][j]) head--;
			q[++head]=dp[i-1][j],loc[head]=j;
			if(loc[tail]<j-2*t) tail++;
			if(j>=t+1) dp[i][j-t]=q[tail]+a[i][j-t];
		}
		for(int j=1;j<=t;j++)
		{
			if(q[tail]<m-t-t+j) tail++;
			dp[i][m-t+j]=q[tail]+a[i][m-t+j];
		}
	}
	for(int i=1;i<=m;i++) ans=max(ans,dp[n][i]);
	printf("%d\n",ans);
	return 0;
}