★ Exercise: repeat a function

Write func repeat(f func(int) int, n int) func(int) int. It returns a function that applies f to its argument n times in a row: repeat(f, 3)(x) is f(f(f(x))).

• repeat(inc, 3)(10) → 13, where inc adds one
• repeat(double, 4)(1) → 16, where double doubles
• repeat(double, 0)(7) → 7

Constraints: n is from 0 to 1000; repeat itself never calls f — only the returned function does; that function may be called many times, and each call applies f exactly n times.

Do not add extra imports unless the task says so explicitly.