#include <stdio.h>
#include <stdlib.h>
/* A binary tree node has data, pointer to left child
   and a pointer to right child */
struct node
{
    int data;
    struct node* left, *right;
};

/* function to create a new node of tree and returns pointer */
struct node* newNode(int data)
{
  struct node* node = (struct node*)
                       malloc(sizeof(struct node));
  node->data = data;
  node->left = NULL;
  node->right = NULL;

  return(node);
}

void fsrednica(struct node* d,int* sciezka,int* srednica) {
    int sciezka1,sciezka2,srednica1,srednica2,pom;
    if(d==NULL) {
        *sciezka=-1;
        *srednica=0;
    }
    else {
        fsrednica(d->left,&sciezka1,&srednica1);
        fsrednica(d->right,&sciezka2,&srednica2);
        *sciezka = (sciezka1>sciezka2) ? sciezka1+1 : sciezka2+1;
        pom = (srednica1>srednica2) ? srednica1 : srednica2;
        *srednica = (pom>(sciezka1+sciezka2+2)) ? pom : (sciezka1+sciezka2+2);
    }
}

int srednicaDrzewa(struct node* d) {
    int sciezka;
    int srednica;
    fsrednica(d,&sciezka,&srednica);

    return srednica;
}

int main()
{
    struct node *root = newNode(1);
    root->left        = newNode(2);
    root->right       = newNode(3);
    root->left->left  = newNode(4);
    root->left->right = newNode(5);

    printf("%d",srednicaDrzewa(root));
    return 0;
}