template<class InputIterator1, class InputIterator2, class T>
constexpr T inner_product(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, T init);
template<class InputIterator1, class InputIterator2, class T,
class BinaryOperation1, class BinaryOperation2>
constexpr T inner_product(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, T init,
BinaryOperation1 binary_op1,
BinaryOperation2 binary_op2);