Maximum element between two nodes of a BST

maxbtw2nodes.c

#include<stdio.h>
#include<stdlib.h>
#include<limits.h>
struct node{
int data;
struct node *left;
struct node *right;
};

struct node *newnode(int x)
{
 struct node* ptr=(struct node*)malloc(sizeof(struct node));
    ptr->data=x;
    ptr->left=NULL;
    ptr->right=NULL;
    return ptr;
}

struct node* insert(struct node *root,int x)
{

struct node* par;
    if(root==NULL)
    {
        root=newnode(x);
        return root;
    }
    else
    {
        struct node *proot=root;
        while(proot!=NULL)
        {

            if(x<proot->data)
            {
                par=proot;
                proot=proot->left;

            }
            else
            {
                par=proot;
                proot=proot->right;

            }
        }
         if(x<par->data)
        par->left=newnode(x);
    else
        par->right=newnode(x);

        return root;
    }

}

void display(struct node *root)
{

    if(root==NULL)
        return;
    display(root->left);
    printf("%d\t",root->data);
    display(root->right);
}
struct node* findlca(struct node *root,int a,int b)
{
    if(root==NULL)
        return NULL;

    if(a>root->data&&b>root->data)
        return findlca(root->right,a,b);

    if(a<root->data&&b<root->data)
        return findlca(root->left,a,b);

    return root;
}
int max(int a,int b)
{
    return (a>b?a:b);
}
int findmax(struct node *root,int k)
{
    int mx=INT_MIN;
    while(root->data!=k)
    {
        if(k<root->data)
        {
            mx=max(mx,root->data);
            root=root->left;

        }
        else
        {
             mx=max(mx,root->data);
            root=root->right;
        }
    }
    return max(mx,k);
}
int main()
{
        int x,a,b;
        struct node *root=NULL;
        while(1)
        {

            scanf("%d",&x);
            if(x==-1)
            break;

            root=insert(root,x);
        }

        display(root);
        printf("\n enter the value of a and b ");
        scanf("%d%d",&a,&b);
        struct node *lca=findlca(root,a,b);
        int max1=findmax(lca,a);
        int max2=findmax(lca,b);
        printf("\n the maximum node in between is %d",max(max1,max2));
}