using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;
class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var map = NArr(n);
        var ans = 0L;
        var asum = 0L;
        var bsum = 0L;
        for (var i = n - 2; i >= 0; --i)
        {
            asum += map[i + 1][0];
            bsum += map[i + 1][1];
            ans += Math.Max(map[i][0] * bsum, map[i][1] * asum);
        }
        WriteLine(ans);
    }
}