The area of a polygon
Very easy
Execution time limit is 1 second
Runtime memory usage limit is 64 megabytes
Determine the area of the polygon.
Input
The first line of one number - N (3 ≤ N ≤ 100000). Next N lines in a pair of numbers - the coordinates of another vertex simple polygon in order to circumvent or counterclockwise. All coordinates are integers modulo not exceeding 10000.
Output
One number - the area of the reduced polygon with an accuracy of 1 decimal places.
Examples
Input #1
Answer #1
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