#include <bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//#pragma GCC optimize("unroll-loops")
//#pragma GCC optimize("-O3")
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("fast-math")
//#pragma GCC optimize("no-stack-protector")
#define F first
#define S second
#define sz(x) int(x.size())
#define pb push_back
#define pf push_front
#define N 100100
#define M ll(1e9 + 7)
#define inf 1e9 + 1e9
using namespace std;
//using namespace __gnu_pbds;
typedef long double ld;
typedef long long ll;
typedef short int si;
typedef array <int, 3> a3;
//typedef tree <int, null_type, less_equal<int>, rb_tree_tag, tree_order_statistics_node_update> ordered_set;
int main()
{
////freopen("input.txt", "r", stdin); //freopen("output4.txt", "w", stdout);
ios_base::sync_with_stdio(0); istream::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n;
cin >> n;
vector <pair <int, int> > g(n);
for (int i = 0; i < n; i++) cin >> g[i].F >> g[i].S;
sort(g.begin(), g.end());
int mx = 0;
vector <pair <int, int> > pr; pr.clear();
for (int i = n - 1; i >= 0; i--)
{
if (g[i].S > mx) pr.pb(g[i]);
mx = max(mx, g[i].S);
}
g = pr;
ll lst = 0;
ll ans = 0;
sort(pr.begin(), pr.end());
for (int i = 0; i < sz(pr); i++)
{
ans += (ll(pr[i].F) - lst) * ll(pr[i].S);
lst = pr[i].F;
}
cout << ans << endl;
}
