Correct
只要功夫深，铁杵磨成针
/ zhǐyào gōngfu shēn, tiě chǔ mó chéng zhēn /
Strokes
Definition
If you work at it hard enough, you can grind an iron bar into a needle./cf idiom 磨杵成针, to grind an iron bar down to a fine needle (idiom); fig. to persevere in a difficult task/to study diligently
Example
Definition
constant grinding turns an iron rod into a needle; constant dropping/dripping wears away a stone; little strokes fell great oaks