```/* F07UE_A1W_F C++ Header Example Program.
*
* Copyright 2019 Numerical Algorithms Group.
* Mark 27, 2019.
*/

#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 << "F07UE_A1W_F C++ Header Example Program Results\n\n";
// Skip heading in data file
string mystr;
getline (cin, mystr);

// Read problem size and number of right-hand-sides
Integer n, nrhs;
cin >> n;
cin >> nrhs;

// Allocate arrays containing A and its factorized form, B
// and the solution X.
double            *ar, *xr=0;
ar  = new double            [n*n];
xr  = new double            [n*nrhs];

// Read the lower triangular matrix A, register and copy
double dd;
for (int i = 0; i<n; ++i) {
Integer l = 0;
for (int j = 0; j<=i; ++j) {
cin >> dd;
Integer k = l + i;
a[k].value = dd;
a[k].id = 0;
ax[k] = a[k];
l = l + (n-j-1);
}
}
// Read the right-hand-sides, register and copy
for (int i = 0; i<n; ++i) {
for (int j = 0; j<nrhs; ++j) {
cin >> dd;
int k = i + j*n;
b[k].value = dd;
b[k].id = 0;
x[k] = b[k];
}
}

// Create AD configuration data object
ifail = 0;

// Solve the system
ifail = 0;

// Print solution
for (int i = 0; i<n; i++) {
for (int j = 0; j<nrhs; j++) {
int k = i + j*n;
}
}
cout << endl;
NagError  fail;
INIT_FAIL(fail);
x04cac(Nag_ColMajor,Nag_GeneralMatrix,Nag_NonUnitDiag,n,nrhs,xr,n,
"  Solution",0,&fail);

cout << "\n\n Derivatives calculated: First order adjoints\n";
cout << " Computational mode    : algorithmic\n";
cout << "\n Derivatives of  x w.r.t first column of b:\n";

// Obtain derivatives
for (int i=0; i<n; i++) {

double inc = 1.0;
ifail = 0;

for (int j=0; j<n; j++) {
ar[i+j*n] = dd;
}
}
// Print derivatives
cout << endl;
INIT_FAIL(fail);
x04cac(Nag_ColMajor,Nag_GeneralMatrix,Nag_NonUnitDiag,n,n,ar,n,
"  Derivatives dX(i,1)/db(j,1)",0,&fail);

// Remove computational data object and tape
ifail = 0;