#!/usr/bin/env python3

# WA: Always uses max frame rate.
n, m = [int(i) for i in input().split()]
xs = [int(i) for i in input().split()]

optt = 0
for x in xs:
    if (m * x) % 1000 == 0:
        optt += (m * x) // 1000
    else:
        optt += 1 + (m * x) // 1000
optt /= m
print(optt)