header function of accumulate in c++ code example

Example 1: accumulate() in c++

accumulate(first, last, sum);
first, last : first and last elements of range 
              whose elements are to be added
              suppose array is 'a'.
sum :  initial value of the sum
Eg: int sum=0;
	accumulate(a.begin(),a.end(),sum);

Example 2: accumulate in cpp

accumulate(start, end, initial_sum);