```/* nag_sum_convcorr_real (c06fkc) Example Program.
*
* Copyright 2019 Numerical Algorithms Group.
*
* Mark 27.0, 2019.
*/

#include <nag.h>
#include <stdio.h>

int main(void)
{
/* Scalars */
Integer exit_status = 0, j, n;
/* Arrays */
double *xa = 0, *xb = 0, *ya = 0, *yb = 0;
/* Nag Types */
NagError fail;

INIT_FAIL(fail);

printf("nag_sum_convcorr_real (c06fkc) Example Program Results\n");
scanf("%*[^\n]" "%" NAG_IFMT "%*[^\n]", &n);
if (n < 2) {
printf("Invalid n.\n");
exit_status = 1;
return exit_status;
}

if (!(xa = NAG_ALLOC(n, double)) ||
!(xb = NAG_ALLOC(n, double)) ||
!(ya = NAG_ALLOC(n, double)) || !(yb = NAG_ALLOC(n, double)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

for (j = 0; j < n; ++j) {
scanf("%lf%lf", &xa[j], &ya[j]);
xb[j] = xa[j];
yb[j] = ya[j];
}

/* nag_sum_convcorr_real (c06fkc).
* Circular convolution or correlation of two real vectors
*/
nag_sum_convcorr_real(Nag_Convolution, xa, ya, n, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_sum_convcorr_real (c06fkc).\n%s\n", fail.message);
exit_status = 2;
goto END;
}
/* nag_sum_convcorr_real (c06fkc), see above. */
nag_sum_convcorr_real(Nag_Correlation, xb, yb, n, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_sum_convcorr_real (c06fkc).\n%s\n", fail.message);
exit_status = 3;
goto END;
}

printf("\n          Convolution   Correlation\n\n");
for (j = 0; j < n; ++j)
printf("%5" NAG_IFMT " %13.5f %13.5f\n", j, xa[j], xb[j]);

END:
NAG_FREE(xa);
NAG_FREE(xb);
NAG_FREE(ya);
NAG_FREE(yb);

return exit_status;
}
```