import math

def nCr(n, r):
    """Return combinations."""
    return math.comb(n, r)

print(nCr(5, 2))

import math

def calculate_nCr(n, r):
    """
    Calculates the number of combinations (nCr) using the formula: n! / (r! * (n-r)!).

    Args:
        n (int): The total number of items available.
        r (int): The number of items to choose.

    Returns:
        int: The number of combinations, or 0 if r > n.
    """
    if r < 0 or r > n:
        return 0  # Invalid input for combinations
    
    # Using math.comb for efficiency in Python 3.8+
    # For older Python versions, manual factorial calculation would be needed
    # return math.factorial(n) // (math.factorial(r) * math.factorial(n - r))
    return math.comb(n, r)

# Example Usage:
n_val = 5
r_val = 2
result = calculate_nCr(n_val, r_val)
print(f"The number of combinations for C({n_val}, {r_val}) is: {result}")

n_val_2 = 10
r_val_2 = 3
result_2 = calculate_nCr(n_val_2, r_val_2)
print(f"The number of combinations for C({n_val_2}, {r_val_2}) is: {result_2}")

n_val_3 = 4
r_val_3 = 5
result_3 = calculate_nCr(n_val_3, r_val_3)
print(f"The number of combinations for C({n_val_3}, {r_val_3}) is: {result_3}")