```/* F11BD_P0W_F C++ Header Example Program.
*
* Copyright 2020 Numerical Algorithms Group.
* Mark 27.1, 2020.
*/

#include <nag.h>
#include <nagx04.h>
#include <stdio.h>
#include <string>
#include <iostream>
using namespace std;

int main(void)
{
int       exit_status = 0;
Integer   ifail = 0;

cout << "F11BD_P0W_F C++ Header Example Program Results\n\n";
// Skip heading in data file
string mystr;
getline (cin, mystr);

Integer n, m;
double  alpha;
cin >> n;
cin >> m;
cin >> alpha;

// Allocate arrays containing A and its factorized form, B
// and the solution X.
double  *b=0, *x=0, *work=0;
Integer lwork = 2*m*n + 1000;

b    = new double [n];
x    = new double [n];
work = new double [lwork];

double bb, b1, a, c;

b1 = 12.0;
a  = 1.0;
c  = 1.0;
bb = b1 - 2.0;

ifail = 0;
for (int i=0; i<n; ++i) {
b[i] = b1*(i+1);
x[i] = 3.0;
}
b[n-1] = b[n-1] - (n+1);

b[0] = b[0] + (b1-1.0)*alpha;
for (int i=1; i<n-1; ++i) {
b[i] = b[i] + b1*alpha;
}
b[n-1] = b[n-1] + (b1-1.0)*alpha;

// Initialize rthe solver
Integer iterm = 2, maxitn = 800, monit = 0, lwreq = lwork;
double  sigmax = 0.0, anorm;
double  tol = 1.0e-10;
ifail = 0;
anorm,sigmax,monit,lwreq,work,lwork,ifail,6,1,1,1);

// Reverse communication call of solver
Integer irevcm = 0;
double  wgt[1];

while (irevcm != 4) {
ifail = 0;
if (irevcm != 4) {
ifail = -1;
if (irevcm == -1) {
//  b = A^Tx
b[0] = bb*x[0] + a*x[1];
for (int i=1; i<n-1; ++i) {
b[i] = c*x[i-1] + bb*x[i] + a*x[i+1];
}
b[n-1] = c*x[n-2] + bb*x[n-1];
}
if (irevcm == 1) {
// b = Ax
b[0] = bb*x[0] + c*x[1];
for (int i=1; i<n-1; ++i) {
b[i] = a*x[i-1] + bb*x[i] + c*x[i+1];
}
b[n-1] = a*x[n-2] + bb*x[n-1];
}
if (irevcm == 2) {
for (int i=0; i<n; ++i) {
b[i] =  x[i]/bb;
}
}
}
}

cout.setf(ios::scientific,ios::floatfield);
cout.precision(2);

cout << "  Solution vector   Residual vector\n";
for (int i=0;i<n;++i) {
cout.width(12);cout << x[i] << "     ";
cout.width(13);cout << b[i] << endl;
}

delete [] b;
delete [] x;
delete [] work;

return exit_status;
}
```