import math

s = input().split()

N, n = int(s[0]), int(s[1])
A, om = float(s[0]), float(s[1])

big_list = []
small_list = []
k_list = []
x_list = []
xt_list = []
f_list = []
k=0

for _ in range(N):
    t, xt = map(float, input().split())
    big_list.append((t, xt, A*math.sin(om*t)))
    xt_list.append(xt)

for i in range(k, N):
    k_list.append(sum([i[1] for i in big_list[i-n:i]])/len(big_list[i-n:i]) if i-n>=0 else 0)


D_old = sum([(((i[2]-i[1])**2)/(N-1))for i in big_list])
D_new = sum([
    ((k_list[i]-big_list[i][1])**2)/(N-1)
    for i in range(N)
])
print(big_list)
print(k_list)
print()
print(f_list)
print(xt_list)
print()
print(D_old)
print(D_new)