A. Lazy Caterer Sequencetime limit per test2 secondsmemory limit per test64 megabytesinputstandard inputoutputstandard outputLazy caterer sequence is defined as the maximum number of pieces formed when slicing a convex pancake with n cuts (each cut is a straight line). The formula is Cn = n·(n + 1) / 2 + 1. You are given n; calculate n-th element of the sequence.InputThe only line of the input contains an integer n (0 ≤ n ≤ 100).OutputOutput the n-th element of lazy caterer sequence.ExamplesInput2Output4Input5Output16
Input2
Output4
['*special problem', '*1300']