Fuzija dva niza u prvi uneti niz

#include <stdio.h>
#define N 100

/* run this program using the console pauser or add your own getch, system("pause") or input loop */

void main()
{
    while(1)
        {
            int na,nb,ia,ib,ic;
            printf("Unesite duzinu niza na: "); scanf("%d",&na);
            if (na<0 || na>N) break;
            printf("Unesite elemente niza a: "); int a[2*N];
            for(ia=0; ia<na; scanf("%d",&a[ia++]));
            if (na==0) printf("\n");

            printf("Unesite duzinu niza nb: "); scanf("%d",&nb);
            if (nb<0 || nb>N) break;
            printf("Unesite elemente niza b: "); int b[N];
            for(ib=0; ib<nb; scanf("%d",&b[ib++]));
            if (na==0) printf("\n");

            ia = na - 1, ib = nb -1, ic = (na+=nb) -1;
            while (ia>=0 && ib >=0) a[ic--] = (a[ia]>b[ib]) ? a[ia--] : b[ib--];
            while (ib >= 0 ) a[ic--] = b[ib--];
            printf("\nNiz nakon obrade izgleda ovako: "); for(ia=0; ia<na; printf("%d ",a[ia++]));
            printf("\n\n");
        }
}