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

typedef long long ll;

int main() {
	int n;
	scanf("%d", &n);

	vector<pair<ll, ll>> in;
	for (int i = 0,a,b; i < n; i++) {
		scanf("%d %d", &a, &b);
		in.push_back({a, b});
	}

	sort(in.begin(), in.end());

	vector<pair<ll, ll>> v;
	for (auto p : in) {
		while (!v.empty() && p.second >= v.back().second)
			v.pop_back();
		v.push_back(p);
	}

	n = v.size();

	vector<ll> dp;
	dp.push_back(v[0].first * v[0].second);

	vector<pair<int, int>> opt;
	opt.push_back({0, 1});
	int curOpt = 0;

	// i >= a >= b
	auto isbetter = [&v, &dp](int a, int b, int i) {
		ll dpa = v[i].first * v[a].second + (a > 0 ? dp[a-1] : 0);
		ll dpb = v[i].first * v[b].second + (b > 0 ? dp[b-1] : 0);

		return dpa <= dpb;
	};

	for (int i = 1; i < n; i++) {
		if (curOpt+1 < opt.size() && i >= opt[curOpt+1].second)
			curOpt++;

		int j = opt[curOpt].first;

		dp.push_back(min(v[i].first * v[j].second + (j > 0 ? dp[j-1] : 0),
						 v[i].first * v[i].second + dp[i-1]));

		while (!opt.empty() && opt.back().second >= i && isbetter(i, opt.back().first, opt.back().second))
			opt.pop_back();

		if (!opt.empty()) {
			int l = opt.back().second, r = n-1;
			if (!isbetter(i, opt.back().first, r))
				continue;
			while (l < r) {
				int m = (l + r) >> 1;
				if (isbetter(i, opt.back().first, m)) r = m;
				else l = m+1;
			}
			opt.push_back({i, l});
		} else {
			opt.push_back({i, i+1});
		}
	}

	printf("%lld\n", dp.back());
}