Submodule of $\mathbb{Z}$-module with the same rank

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For a $\mathbb{Z}$-module $M$ in the field of algebraic numbers, suppose that it has a $\mathbb{Z}$-submodule $N$ which has the same rank with $M$. Shall one deduce that $M=N$? Or can anyone please supply to me some counterexamples?