\[
\boxed{
\begin{aligned}
- & \quad 3 \text{Fe} + 2 \text{O}_2 \rightarrow \text{Fe}_3\text{O}_4 \\
- & \quad \text{Fe}_3\text{O}_4 + 4 \text{H}_2 \rightarrow 3 \text{FeO} + 4 \text{H}_2\text{O} \\
- & \quad \text{FeO} + \text{H}_2 \rightarrow \text{Fe} + \text{H}_2\text{O}
\end{aligned}
}
\]