import statistics
import math

X = [95, 85, 80, 70, 60]
Y = [85, 95, 70, 65, 70]

mean_x = statistics.mean(X)
mean_y = statistics.mean(Y)

diff_x = 0
diff_y = 0
for i in range(len(X)):
    diff_x += pow(X[i] - mean_x, 2)
    diff_y += pow(Y[i] - mean_y, 2)
    
stand_dev_x = math.sqrt(1 / len(X) * diff_x)
stand_dev_y = math.sqrt(1 / len(Y) * diff_x)

sum = 0
for i in range(len(X)):
    sum += ((X[i] - mean_x) / stand_dev_x ) * ((Y[i] - mean_y) / stand_dev_y)
    
r = 1 / len(X) * sum

b = r * stand_dev_y / stand_dev_x
a = mean_y - b * mean_x

answer = a + b * 80

print(round(answer, 3))