Trailing Return Type with decltype

Write a function template add(T first, U second) whose return type is written AFTER the parameter list with the trailing-return syntax:

auto add(T first, U second) -> decltype(first + second)

Here auto is only a placeholder; decltype(first + second) tells the compiler to use whatever type the addition produces, and it may name the parameters because they are declared to its left. The tests print add(2, 3), add(2, 2.5), add(1.5, 2) and add(std::string("tem"), std::string("plate")) on separate lines.

Do NOT write a main function.