#include<bits/stdc++.h>
using namespace std;
const int N=5100;
struct tree {int a,b;}tr[2*N];
int f[N][N],q[N];
int main() 
{
    int n,d,m;scanf("%d%d%d",&n,&d,&m);
    for(int i=1; i<=n; i++)scanf("%d%d",&tr[i].a,&tr[i].b);
    memset(f,0,sizeof(f));
    int ans=f[1][0]=tr[1].a;
    for(int j=1; j<=m; j++) 
	{
        int l=1,r=1;q[1]=0;
        for(int i=1; i<=n; i++) 
		{
            while(l<=r && tr[i].b-tr[q[l]].b >d )l++;
			f[i][j]=(l<=r)?f[q[l]][j-1] + tr[i].a:0;ans=max(ans,f[i][j]);
			while(l<=r && f[q[r]][j-1]<=f[i][j-1])r--;
            if(f[i][j-1])q[++r]=i; 
        }
    }
    printf("%d\n",ans);
    return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int N=5100;
struct tree {int a,b;}tr[2*N];
int f[N][N],q[N];
int main() 
{
    int n,d,m;scanf("%d%d%d",&n,&d,&m);
    for(int i=1; i<=n; i++)scanf("%d%d",&tr[i].a,&tr[i].b);
    memset(f,0,sizeof(f));
    int ans=f[1][0]=tr[1].a;
    for(int j=1; j<=m; j++) 
	{
        int l=1,r=1;q[1]=0;
        for(int i=1; i<=n; i++) 
		{
            while(l<=r && tr[i].b-tr[q[l]].b >d )l++;
			f[i][j]=(l<=r)?f[q[l]][j-1] + tr[i].a:0;ans=max(ans,f[i][j]);
			while(l<=r && f[q[r]][j-1]<=f[i][j-1])r--;
            if(f[i][j-1])q[++r]=i; 
        }
    }
    printf("%d\n",ans);
    return 0;
}