it ends when it sayscout << "how to get the protons and neutrons of an element (a) Atomic mass atomic number (b) atomic number atomic mass";
it ends when it says
cout << "how to get the protons and neutrons of an element (a) Atomic mass atomic number (b) atomic number atomic mass";
Of course it does. That's the last instruction. Nothing follows, except the return statement
Add instructions that calculate atomic mass and number?