BOJ - 6850 - Cows

import sys
import math

def getDegree(p1, p2):
    return p2[0] - p1[0], p2[1] - p1[1]

def ccw(p1, p2, p3):
    v, u = getDegree(p1, p2), getDegree(p2, p3)
    if v[0] * u[1] > v[1] * u[0]: return True
    else: return False

def convex_hull(position):
    convex = []
    for p3 in position:
        while len(convex) >= 2:
            p1, p2 = convex[-2], convex[-1]
            if ccw(p1, p2, p3):
                break
            convex.pop()
        convex.append(p3)
    return convex

def getWidth(p1, p2, p3):
    return(
        abs((p2[0] - p1[0]) * (p3[1] - p1[1]) - (p3[0] - p1[0]) * (p2[1] - p1[1])) // 2
    )

def solution():
    N = int(sys.stdin.readline())

    position = []
    for _ in range(N):
        x, y = map(str, sys.stdin.readline().split())
        position.append((int(x), int(y)))

    position = sorted(position, key=lambda x:(x[0], x[1]))
    ccwtemp = convex_hull(position)

    position.reverse()
    temp = convex_hull(position)

    for i in range(1, len(temp)):
        ccwtemp.append(temp[i])

    ret = 0
    for i in range(1, len(ccwtemp) - 2):
        ret += getWidth(ccwtemp[0], ccwtemp[i], ccwtemp[i+1])

    print(ret // 50)


solution()

https://www.acmicpc.net/problem/6850