C++ :

#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll n, d, k;
ll dp[500005];
struct gezi
{
	ll pos;
	ll zhi;
}a[500005];
bool check(int m)
{
	ll maxx = d + m;
	ll minn = d - m;
	if (minn <= 0)minn = 1;
	memset(dp, -128, sizeof(dp));
	dp[0] = 0;
	for (int i = 1; i <= n; i++)
	{
		for (int j = i - 1; j >= 0; j--)
		{
			if (a[i].pos - a[j].pos < minn)continue;
			if (a[i].pos - a[j].pos > maxx)break;
			dp[i] = max(dp[i], dp[j] + a[i].zhi);
			if (dp[i] >= k)
			{
				return 1;
			}
		}
	}
	return 0;
}
int main()
{
	cin >> n >> d >> k;
	int sum = 0;
	int ans = -1;
	a[0].pos = 0;
	a[0].zhi = 0;
	for (int i = 1; i <= n; i++)
	{
		cin >> a[i].pos >> a[i].zhi;
		if (a[i].zhi > 0)
		{
			sum += a[i].zhi;
		}
	}
	int l = 0, r = 1005;
	int mid;
	while (l < r)
	{
		mid = (l + r) / 2;
		if (check(mid))
		{
			r = mid;
			ans = r;
		}
		else
		{
			l = mid + 1;
		}
	}
	cout << ans << endl;
}