# https://yukicoder.me/problems/no/1986

N = int(input())
# 美味しい:1 , 普通:0
candy = [1 if i % 2 == 0 else 0 for i in range(N)]
# print(candy)
F = []
S = []
i = 1
while len(candy) > 1:
    if i % 2 == 1:
        if candy[0] == 1:
            F.append(candy.pop(0))
        elif candy[-1] == 1:
            F.append(candy.pop(-1))
        # else:
        #     F.append(candy.pop(0))
        print(f"F_list: {F}")
    else:
        if candy[0] == 1:
            S.append(candy.pop(0))
        elif candy[-1] == 1:
            S.append(candy.pop(-1))
        # else:
        #     S.append(candy.pop(0))
    print(f"S_list: {S}")
    i += 1
print(len(F))