Tree t6=new Tree();
        t6.data=6;
        Tree t7=new Tree();
        t7.data=7;
        Tree t3=new Tree();
        t3.data=3;
        t3.left=t6;
        t3.right=t7;




        Tree t4=new Tree();
        t4.data=4;
        Tree t5=new Tree();
        t5.data=5;
        Tree t2=new Tree();
        t2.data=2;
        t2.left=t4;
        t2.right=t5;
        Tree t1=new Tree();
        t1.data=1;
        t1.left=t2;
        t1.right=t3;