Python
# Program to check friendly pair
def abundancy_index(n: int) -> float:
total = 0
for i in range(1, n + 1):
if n % i == 0:
total += i
return total / n
a = int(input("Enter first number: "))
b = int(input("Enter second number: "))
if a <= 0 or b <= 0:
print("Numbers must be positive.")
else:
if abundancy_index(a) == abundancy_index(b):
print(a, "and", b, "form a friendly pair")
else:
print(a, "and", b, "do not form a friendly pair")Output
Enter first number: 6 Enter second number: 28 6 and 28 form a friendly pair
Two numbers are friendly if the ratio (sum of divisors / number) is equal for both. We implement a helper function to compute the abundancy index and compare for the two inputs.