import math

n = 5     # number of trials (flips)
p = 0.5   # probability of heads on each flip
k = 3     # exactly 3 heads

probability = math.comb(n, k) * (p ** k) * ((1 - p) ** (n - k))
print(f"P(X = {k}) = {probability:.4f}")  # 0.3125