import math



x1, y1, x2, y2 = list(map(float, input().split(' ')))



print(('{:.5f}'.format(math.sqrt((x2-x1)**2+(y2-y1)**2))))
import math



def main():

    x1, y1, x2, y2 = [float(n) for n in input().split()]



    d = math.sqrt((x2 - x1)**2 + (y2 - y1)**2)



    print(("{:.5f}".format(d)));



if __name__ == '__main__':

    main()

import math

x1, y1, x2, y2 = list(map(float, input().split(" ")))
print(("{:.5f}".format(math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2))))

import math


def main():
    x1, y1, x2, y2 = [float(n) for n in input().split()]
    d = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)
    print(("{:.5f}".format(d)))


if __name__ == "__main__":
    main()

-x1, y1, x2, y2 = list(map(float, input().split(" "))) -print(("{:.5f}".format(math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2)))) + +def main(): +    x1, y1, x2, y2 = [float(n) for n in input().split()] +    d = math.sqrt((x2 - x1) ** 2 + (y2 - y1) ** 2) +    print(("{:.5f}".format(d))) + + +if __name__ == "__main__": +    main()