Submission #4760

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Source Code Expand

#!/usr/bin/env python
# -*- coding:utf-8 -*-

import sys
import decimal
from decimal import Decimal
from math import sqrt

# decimal.getcontext().prec = 20

N = int(sys.stdin.readline())
start, goal = [Decimal(_) for _ in sys.stdin.readline().split(' ')]

roads = []
for i in xrange(N+1):
    roads += [[Decimal(_) for _ in sys.stdin.readline().split(' ')]]

pos = start
stay_count = 1
distance = Decimal(0.0)
for r in xrange(N):
    next_pos = pos + (goal - pos) / (N - r)
    if next_pos < roads[r + 1][0]:
        distance += ((roads[r + 1][0] - pos) ** 2 + stay_count ** 2).sqrt()
        pos = roads[r + 1][0]
        stay_count = 1
    elif roads[r + 1][1] < next_pos:
        distance += ((pos - roads[r + 1][1]) ** 2 + stay_count ** 2).sqrt()
        pos = roads[r + 1][1]
        stay_count = 1
    else:
        stay_count += 1
else:
    stay_count -= 1

distance += (abs(goal - pos) ** 2 + (stay_count) ** 2).sqrt()

print distance

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