INPUT       endpoints a, b; even positive integer n
       OUTPUT   approximate XI  to  I
             Step 1  Set   h = (b-a)/n
             Step 2  Set   XI0 = f(a) + f(b); XI1 = 0; XI2 = 0;
             Step 3   For i = 1, ..., n-1 do Steps 4 and 5.
                         Step 4   Set X = a + i h.
                          Step 5  If  i  is even then set XI2 = XI2 + f(x) else set XI1 = XI1 + f(x).
             Step 6  Set   XI = h(XI0+2*XI2+4*XI1)/3
             Step 7  Ouput(XI)
                         Stop
 

Problem: Using above algorithm to compute 

Requirement:
(a) Read the datas  a, b, and  n  from the file input_parameter.dat
(b) Use the command function to define f(x) and the command subroutine to implement the algorthm.
(c) Use double precision for real number to compute the result.