Let \(\omega \) be a closed \(n\)-form on a smooth manifold \(M\) . Let \(N\) be a compact, orientable \(n\)-manifold without boundary and \(f:N\to M\) a smooth map with
\[ \int _N f^*\omega \ne 0. \]
Show that deRham cohomology group \(H^n_{dR}(M)\) is not trivial.