Numere lipsa

#include <stdio.h>
#include <stdlib.h>

typedef struct NOD{
    int nr;
    struct NOD *next;
}NOD;

NOD *creare_nod(int nr){
    NOD *nod_nou = malloc(sizeof(NOD));
    nod_nou -> nr = nr;
    nod_nou -> next = NULL;
    return nod_nou;
}

NOD *adauga_numar(NOD *head, int nr){
    NOD *nr_nou = creare_nod(nr), *nod = head;

    if(head == NULL)
        return nr_nou;
    if(head -> nr > nr){
        nr_nou -> next = head;
        return nr_nou;
    }
    while(nod->next && nod ->next ->nr < nr) nod = nod-> next;
    nr_nou -> next = nod->next;
    nod -> next = nr_nou;

    return head;
}

int numere_lipsa(NOD *head, int n){
    int nr = head -> nr - 0;
    NOD *nod = head;
    for(; nod -> next; nod = nod -> next){
        if(nod -> next -> nr - nod -> nr > 1)
            nr += (nod -> next -> nr - nod -> nr -1);
    }
    nr += n - nod->nr;
    return nr;
}
int main(){
    int n, nr = 0, num;
    NOD *numere = NULL;
    scanf("%d", &n);

    while(scanf("%d", &num) != EOF){
        numere = adauga_numar(numere, num);
    }

    nr = numere_lipsa(numere, n);
    printf("%d", nr);
}