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ISCO(ICPC Steel Company) is a company that buys steel sheets of a certain shape, cuts them into pieces, and sells them in the industry market. Every steel sheet that ISCO buys is a polygon without holes such that each side is either horizontal or vertical with respect to the x-axis. The length of each side is a positive integer. We call such a polygon a histogon. See Figure 1(a) for a histogon.
Figure 1. (a) A steel sheet which is a histogon. (b) An axis-aligned rectangle (red) with maximum area contained in the histogon. (c) The histogon is subdivided along vertical lines into 8 rectangular slabs with width 1.
Since the market price of a piece becomes much higher if the piece is a rectangle with larger area, it is desirable to cut a steel sheet so as to get a rectangle of maximum area. Thus, the task is to find a rectangle contained in a steel sheet with largest area. We assume that the rectangle should be axis-aligned, that is, every side is horizontal or vertical with respect to the x-axis. Formally, this problem can be stated as follows. Given a histogon, find an axis-aligned rectangle with maximum area contained in the histogon. Figure 1(b) shows an axis-aligned rectangle with maximum area that is contained in the histogon in Figure 1(a).
A histogon with width n can be subdivided along vertical lines into n rectangular slabs with width 1. The histogon in Figure 1(a) can be subdivided along vertical lines into 8 rectangular slabs, as shown in Figure 1(c). These slabs are numbered from 1 to n in order along the x-axis such that the leftmost slab has number 1. To ease the description, we assume that the x-axis intersects every slab. The x-axis intersects every slab in Figure 1(c). Then, slab i can be represented by two values, hi and li, where hi denotes the vertical length of slab i lying above the x-axis and li denotes the vertical length of slab i lying below the x-axis.
Given a histogon with width n, write a program to output the maximum area among the axis-aligned rectangles contained in the histogon.
Your program is to read from standard input. The input starts with a line containing one integer n (1 ≤ n ≤ 200,000), where n is the width of the input histogon. The slabs are numbered from 1 to n such that the leftmost slab has number 1. In the following n lines, the i-th line contains 2 nonnegative integers that represent hi and li (0 ≤ hi, li ≤ 1,000,000,000).
Your program is to write to standard output. Print exactly one line. The line should contain the maximum area among rectilinear rectangles contained in the given histogon.
8 1 4 4 2 3 2 5 1 6 4 4 2 2 3 5 0
5 23 15 23 17 3 22 15 3 5 1