import math

n,k = list(map(int, input().split()))

a = list(map(int, input().split()))

m = a.index(min(a))

print((math.ceil((len(a)-1)/(k-1))))
import math

print(((lambda x:math.ceil((int(x[0])-1)/(int(x[1])-1)))(input().split())))
import math

n, k = list(map(int, input().split()))
a = list(map(int, input().split()))
m = a.index(min(a))
print((math.ceil((len(a) - 1) / (k - 1))))

import math

print(((lambda x: math.ceil((int(x[0]) - 1) / (int(x[1]) - 1)))(input().split())))

-n, k = list(map(int, input().split())) -a = list(map(int, input().split())) -m = a.index(min(a)) -print((math.ceil((len(a) - 1) / (k - 1)))) +print(((lambda x: math.ceil((int(x[0]) - 1) / (int(x[1]) - 1)))(input().split())))