import math import sys def main(): input = sys.stdin.read().split() n = int(input[0]) xs = list(map(int, input[1:n+1])) sum_ = 0.0 compensation = 0.0 for x in xs: s = math.sqrt(x) # Kahan summation steps y = s - compensation t = sum_ + y compensation = (t - sum_) - y sum_ = t # Print with 17 decimal places print("{0:.17f}".format(sum_)) if __name__ == "__main__": main()