Safest Pens Bessie and her cow compatriots feel safest when they are surrounded by a fence -- and even safer when surrounded by two fences. On the farm's pastures there are N (1 <= N <= 100,000) rectangular fences. The fences don't overlap or touch, however any given fenced area might wholly contain one or more other areas. Bessie and the other cows want to graze within a pen that is surrounded by as many other pens as possible. Furthermore she wants to know how many of those 'safest places' there exist in the pastures. Help Bessie learn these numbers. PROBLEM NAME: safepens INPUT FORMAT: * Line 1: A single line with the single integer, N * Lines 2..N+1: Each line contains four space-separated integers (respectively X1, Y1, X2 and Y2) that are the coordinates of the lower left and upper right corner of the fences. All coordinates are in the range 1..1,000,000,000 and both X1