#include <bits/stdc++.h>
using namespace std;

long long t, n, l, r, x, k, a, b, nown = 1, nowzs, nowk = 1;
unsigned long long ans;
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin >> t >> n >> l >> r >> x >> k;
	nowzs = l;
	while (t--)
	{
		cin >> a >> b;
		if ((a == 0 && nown == n) || (a == 1 && nown == 1))
		{
			cout << -1;
			return 0;
		}
		if (a == 0)
		{
			nowzs = l;
			nown++;
		}
		if (a == 1)
		{
			nowzs = r;
			nown--;
		}
		if (b == 1)
		{
			nowzs = min(nowzs + x, r);
		}
		ans += nowzs * nown;
		if (nowk == k)
		{
			cout << ans;
			return 0;
		}
		if (nowzs == r)
			nowk++;
		else
			nowk = 0;
	}
	cout << ans;
	return 0;
}