import math as m
D=float(input("Enter the diameter of the bigger pulley = "))
d=float(input("Enter the diameter of the smaller pulley = "))
C=float(input("Enter the distance between the two pulleys = "))
L=(4*(C**2)-(D-d)**2)**0.5+(3.14*(D+d)/2+(D-d)*(m.asin((D-d)/2*C)))
print("The length of the belt needed to wrap around two pulleys =",L)