# Crane Balancing

Wherever there is large-scale construction, you will find cranes that do the lifting. One hardly ever thinks about what marvelous examples of engineering cranes are: a structure of (relatively) little weight that can lift much heavier loads. But even the best-built cranes may have a limit on how much weight they can lift.

The Association of Crane Manufacturers (ACM) needs a program to compute the range of weights that a crane can lift. Since cranes are symmetric, ACM engineers have decided to consider only a cross section of each crane, which can be viewed as a polygon resting on the $x$-axis.

Figure 1 shows a cross section of the crane in the first sample input. Assume that every $1 \times 1$ unit of crane cross section weighs 1 kilogram and that the weight to be lifted will be attached at one of the polygon vertices (indicated by the arrow in Figure 1). Write a program that determines the weight range for which the crane will not topple to the left or to the right.

## Input

The input consists of a single test case. The test case starts with a single integer $n$ ($3 \le n \le 100$), the number of points of the polygon used to describe the crane’s shape. The following $n$ pairs of integers $x_ i, y_ i$ ($-2\, 000 \le x_ i \le 2\, 000, 0 \le y_ i \le 2\, 000$) are the coordinates of the polygon points in order. The weight is attached at the first polygon point and at least two polygon points are lying on the $x$-axis.

## Output

Display the weight range (in kilograms) that can be attached
to the crane without the crane toppling over. If the range is
$[a,b]$, display
$\lfloor a \rfloor $
`..` $\lceil b
\rceil $. For example, if the range is $[1.5,13.3]$, display `1` `..` `14`. If
the range is $[a,\infty
)$, display $\lfloor a
\rfloor $ `..` `inf`. If the crane cannot carry any weight, display
`unstable` instead.

Sample Input 1 | Sample Output 1 |
---|---|

7 50 50 0 50 0 0 30 0 30 30 40 40 50 40 |
0 .. 1017 |

Sample Input 2 | Sample Output 2 |
---|---|

7 50 50 0 50 0 0 10 0 10 30 20 40 50 40 |
unstable |