#!/usr/bin/python
# -*- coding: utf-8 -*-
# By formula derived by Euler(A great mathematician)
print("Euler's Formula: F(faces) + V(vertices) = E(Edges)+2\n")
# Further derivation
print("Derivation 1: E(Edges) = F(faces)+V(vertices) - 2")
print("Derivation 2: V(vertices) = E(edges)+2 - F(Faces)")
print("Derivation 3: F(faces) = E(edges)+2 - V(vertices)")
# By order of operations, parenthesis can be added
# for ensuring, but not needed
def E(f, v):
return f+v - 2
def V(e, f):
return e+2 - f
def F(e, v):
return e+2 - v
# function to evaluate
# By default datatype of raw_input() is string
user = raw_input("\nE, V or F: ").upper()
print(" ")
# evaluating function asked by user
if user == "E":
print("\nEdges: " + str(E(input("Faces: "), input("Vertices: "))))
elif user == "V":
print("\nVertices: " + str(V(input("Edges: "), input("Faces: "))))
elif user == "F":
print("\nFaces: " + str(F(input("Edges: "), input("Vertices: "))))
else:
print("Invalid Input, Try again!")
# A while loop can be added
# to perform multiple calculations