Write a function that checks whether a path with given sum exists in the tree. 

int pathwithsum(Btree B, int sum)
{
    int remaining;
    if(!B)
        return sum==0;
    remaining = sum - B->data;
    if(B->left && B->right || !B->left && !B->right)
        return pathwithsum(B->left, remaining) || pathwithsum(B->right, remaining);
    else
        if(B->left)
            return pathwithsum(B->left, remaining);
        else
            return pathwithsum(B->right, remaining);
    
}