```/* nag_roots_lambertw_complex (c05bbc) Example Program.
*
* Copyright 2019 Numerical Algorithms Group.
*
* Mark 27.0, 2019.
*/

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

int main(void)
{
/* Scalars */
Complex w, z;
double resid;
Integer branch;
Integer exit_status = 0;
char offset[10];
Nag_Boolean offsetenum;
NagError fail;

INIT_FAIL(fail);

printf("nag_roots_lambertw_complex (c05bbc) Example Program Results\n");

/* Skip heading in data file */
scanf("%*[^\n] ");
scanf("%" NAG_IFMT "%*[^\n] ", &branch);
scanf("%9s%*[^\n] ", offset);

/*
* nag_enum_name_to_value (x04nac).
* Converts NAG enum member name to value
*/
offsetenum = (Nag_Boolean) nag_enum_name_to_value(offset);

printf("\n");
printf("branch = %" NAG_IFMT "\n", branch);
printf("offset = %s\n", offset);
printf("\n               z                              w(z)"
"                    resid\n\n");
while (scanf(" (%lf,%lf)%*[^\n] ", &z.re, &z.im) != EOF)
{
/*
* nag_roots_lambertw_complex (c05bbc)
* Values of Lambert's W function, W(z)
*/
nag_roots_lambertw_complex(branch, offsetenum, z, &w, &resid, &fail);
if (fail.code == NE_NOERROR ||
fail.code == NW_REAL || fail.code == NW_TOO_MANY_ITER) {
printf("(%14.5e,%14.5e) (%14.5e,%14.5e) %14.5e\n",
z.re, z.im, w.re, w.im, resid);
}
else {
printf("Error from nag_roots_lambertw_complex (c05bbc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}
}

END:
return exit_status;
}
```