Accumulate the sum of a sequence.
template <class InputIterator, class T> T accumulate(InputIterator first, InputIterator last, T init); template <class InputIterator, class T, class BinaryOperation> T accumulate(InputIterator first, InputIterator last, T init, BinaryOperation binary_op);
The sum of the values in a range or the sum of the values after being processed by an operation is returned.