Find size of a binary tree

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


struct treeNode
{
    int data;
    struct treeNode* left;
    struct treeNode* right;

};


struct treeNode* newNode(int n)
{
    struct treeNode* node = (struct treeNode*) malloc(sizeof(struct treeNode));
    node->data = n;
    node->left = NULL;
    node->right = NULL;
    return  node;

}

int sizeOfTree(struct treeNode* root)
{
    if (root == NULL)
    {
        return 0;
    }

    return sizeOfTree(root->left) + 1 + sizeOfTree(root->right);
}

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

    printf("Size of the tree is %d", sizeOfTree(root));
    getchar();
    return 0;
}