For a positive integer n, Let a(n)=1+12+13+14+…+12n−1.then
a(100)≤100
a(100)>100
a(200)≤100
a(200)>100
It can be proved by induction that n2>a(n)≤n.
∴2002<a(200)⇒a(200)>100 and a(100)≤100.