def distance(a, b):
    x = abs(a[0] - b[0])
    y = abs(a[1] - b[1])
    dis = (x** 2 + y** 2)** 0.5
    return dis

point = [[0, 0]]
get = input()
get = list(map(int, get.split(',')))
num = len(get)// 2
for i in range(num):
    point.append([get[i* 2], get[i* 2 + 1]])

s = 0

for i in range(num):
    s = s + distance(point[i], point[i + 1])

print("%.2f" % s)