I'm currently studying some set theory and I am slightly confused of the terminology in this proposition :
-Suppose that a set A is infinite, and there is an injection f : (Positive Integers) -> A.
-Suppose that we have a bijection c : {1,...,n} -> A.
-Then the composite of c^-1 o f o inc : {1,...,m} -> {1,...,n}.
-I do not understand the inc of the line above. The inc between which two sets?