Intersection Point in Y Shaped Linked Lists

/* Linked List Node
struct Node {
  int data;
  struct Node *next;
  Node(int x) {
    data = x;
    next = NULL;
  }
}; */

//Function to find intersection point in Y shaped Linked Lists.
int length(Node*head)
{
    int i=0;
    Node*temp=head;
    while(temp!=NULL)
    {
        temp=temp->next;
        i++;
    }
    return i;
}
int intersectPoint(Node* head1, Node* head2)
{
    int n=length(head1);
    int m=length(head2);
    Node*ptr1;
    Node*ptr2;
    int d;
    if(n>m)
    {
        d=n-m;
        ptr1=head1;
        ptr2=head2;
        
    }
    else{
        d=m-n;
        ptr1=head2;
        ptr2=head1;
        
    }
    while(d>0){
        if(ptr1==NULL){
           return -1;
        }
         ptr1=ptr1->next;
        d--;
    }
    while(ptr1->next!=NULL && ptr2->next!=NULL)
    {
        if(ptr1==ptr2)
        {
            return ptr1->data;
        }
        ptr1=ptr1->next;
        ptr2=ptr2->next;
    }
    return -1;
}