Let $(M,+,e)$ be a commutative monoid with unit $e$. An element $a\in M$ is called cancellative element if
 
for any $b,c \in M$ such that $a+b=a+c$ implies that $b=c$. 

Let $(\mathbf{N},+,0)$ the commutative monoid of natural numbers. 

suppose that 

 1. we have two morphisms of monoids $f:(\mathbf{N},+,0)\rightarrow (M,+,e)$ and $g:(M,+,e)\rightarrow (\mathbf{N},+,0) $ such that $g\circ f= id$. 
 2. The monoid $(M,+,e)$ is torsion free.

My question is the following: is the element $a=f(1)$ automatically a cancellative element in $(M,+,e)$ ?