Suppose logits are a 3*4 matrix, and the target is a 1*3, how is cross-entropy loss calculated mathematically?

Question

# Example logits matrix (3x4)
logits = np.array([[1.2, 0.5, -0.7, 2.1],
                   [0.8, -1.2, 0.9, 1.5],
                   [0.1, 1.0, -0.5, 0.3]])

# Example target vector (1x3)
target = np.array([5, 2, 1])

I don't need Python code, I need a mathematical illustration.