Problem:
Score : 100 points

Problem Statement

Takahashi wants to print a document with N pages double-sided, where two pages of data can be printed on one sheet of paper.

At least how many sheets of paper does he need?

Constraints

N is an integer.

1 \leq N \leq 100

Input

Input is given from Standard Input in the following format:

N

Output

Print the answer.

Sample Input 1

5

Sample Output 1

3

By printing the 1-st, 2-nd pages on the 1-st sheet, 3-rd and 4-th pages on the 2-nd sheet, and 5-th page on the 3-rd sheet, we can print all the data on 3 sheets of paper.

Sample Input 2

2

Sample Output 2

1

Sample Input 3

100

Sample Output 3

50

Solution in Python (3.4.3) (judge verdict: Runtime Error)

vs = input().split(' ')
N = int(vs[0])
M = int(vs[1])
valueMap = [10 for i in range(M)]

for i in range(N):
  vs = input().split(' ')
  t_i = int(vs[0]) - 1
  t_v = int(vs[1])

  if (valueMap[t_i] > t_v and t_v != 0):
    valueMap[t_i] = t_v
valueMap = list(map(lambda v: 0 if v == 10 else v, valueMap))

if (len(valueMap) != 1 and valueMap[0] == 0):
  print(-1)
else:
  print("".join(map(str, valueMap)))