#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ul = unsigned long;
using ull = unsigned long long;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	int n;
	cin >> n;

	vector<int> a(n - 1), b(n), c(n);

	for (auto&& it : a)
		cin >> it;
	for (int i = 0; i < n; ++i)
		cin >> b[i] >> c[i];

	int res{ 0 };
	int sb{ 0 }, sc{ 0 };
	for (int i = 0; i < n - 1; ++i)
	{
		sb += b[i];
		sc += c[i];
		res += (sc - sb) * a[i];
	}

	cout << res << "\n";

	return 0;
}