Paranoid Cows  (paranoid.X)

Farmer Ran's N cows (1 <= N <= 100,000) conveniently numberd 1..N
are self-conscious about their milk output. A cow who does not
produce much milk is likely to be teased by the other cows.

FR has designed a milking schedule for the cows in which every cow
i is assigned to an interval of time A_i..B_i (0 <= A_i < B_i
<= 1,000,000,000). Each cow i must enter the barn at time A_i for
milking and depart from the barn at time B_i. The door to the barn
is narrow and can accommodate at most one cow at a time, so FJ has
designed his schedule so that no two cows enter or leave at the
same time.

Suppose the milking interval for some cow i contains the interval
for some other cow j.  That is, A_i < A_j < B_j < B_i.  In this
case, we say these two intervals "nest".  Nesting intervals are
bad, since in this case cow i is in the barn for the entire duration
of cow j's milking and as a result, cow i can spy on cow j and
determine her milk output. Since cows are paranoid about other cows
knowing their milk output, FR hopes his schedule does not contain
any nested intervals.

Help FR by determining the largest index K (1 <= K <= N) such the
intervals of cows 1..K have no occurrences of nesting.

PROBLEM NAME: paranoid

INPUT FORMAT:

* Line 1: A single integer: N

* Lines 2..N+1: Line i contains two integers: A_i and B_i

SAMPLE INPUT:

5
7 20
1 4
3 12
6 10
0 3

OUTPUT FORMAT:

* Line 1: A single integer, k.

SAMPLE OUTPUT:

3

OUTPUT DETAILS:

The interval for cow #4 (6-10), is nested within the interval for
cow #3 (3-12).  Furthermore, none of the intervals for cows #1..#3
nest within each other.