#include<iostream>

#include<cstdio>

#include<cmath>

using namespace std;

const int N=;

inline int read(){

    int X=,w=;char ch=;

    while(!isdigit(ch)){w|=ch=='-';ch=getchar();}

    while(isdigit(ch))X=(X<<)+(X<<)+(ch^),ch=getchar();

    return w?-X:X;

}

int f[N][N],q[N];

int main(){

    int n=read(),m=read(),k=read(),t=read();

    for(int i=;i<=k;i++){

        int x=read(),y=read(),v=read();

        f[x][y]=v;

    }

    int maxn=;

    for(int i=;i<=n;i++){

        int l=,r=;

        for(int j=;j<=t;j++){

            while(l<=r&&f[i-][q[r]]<=f[i-][j])r--;

            q[++r]=j;

        }

        for(int j=;j<=m;j++){

            while(l<=r&&q[l]<j-t)l++;

            while(l<=r&&j+t<=m&&f[i-][q[r]]<=f[i-][j+t])r--;

            q[++r]=j+t;

            f[i][j]+=f[i-][q[l]];

            maxn=max(maxn,f[i][j]);

        }

    }

    printf("%d",maxn);

    return ;

}