Lee Dongho's Truck

Lee Dongho wants to store his paintings in a square warehouse whose side length is 200 meters. The north and south sides of the warehouse are walls, while the entire west and east sides are sliding doors, so a truck can enter from the west and leave through the east. A truck's width is an integer number of meters, and inside the warehouse it must move in a straight line without changing direction. The roof is high enough that height never matters.

Inside the warehouse there are pillars supporting the roof. Each pillar is treated as a point with no size. The truck may not pass through or touch any pillar, nor may it pass through or touch the north or south wall.

Given the positions of the pillars, find the maximum possible width of a truck that can pass through the warehouse.

The first line contains the number of pillars N. N is a nonnegative integer not greater than 50.

Each of the next N lines contains the position of one pillar as two integers. The first integer is the distance from the east wall, and the second integer is the distance from the north wall. Both integers are between 0 and 200, inclusive.

Print one integer: the maximum width of a truck that can pass through the warehouse.