787 B | 787 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
# sys.setrecursionlimit(10**7)
BLANK = " "
inp = input
# inp = lambda : sys.stdin.readline().rstrip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def gcd(a, b): return gcd(b, a % b) if b > 0 else a
def lcm(a, b): return a * b // gcd(a, b)
def solve():
n, k = mii()
l = mii()
ans = 1e10
for start in range(1, 2000):
cnt = 0
for j in range(n):
ob = start + j * k
diff = abs(ob - l[j])
if diff > 0:
cnt += 1
ans = min(ans, cnt)
p(ans)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()