Given a chemical equation as a string of molecules with optional coefficients and element counts, decide whether it is balanced.

A reaction is written 'molecule (+ molecule)* = molecule (+ molecule)*'. A molecule is an optional positive integer coefficient (at most 1000) followed by element symbols, each with an optional positive integer count (for example 12Cu is twelve copper atoms). Decide whether the equation is balanced, that is, each element has the same total number of atoms on both sides.