# Factorial GCD

Evaluate $\gcd ( 19 ! + 19, 20! + 19 )$.

Details and assumptions

The number $n!$, read as n factorial, is equal to the product of all positive integers less than or equal to $n$. For example, $7! = 7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1$.

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