Below we will define an n-interesting polygon. Your task is to find the area of a polygon for a given n.
A 1-interesting polygon is just a square with a side of length 1. An n-interesting polygon is obtained by taking the n - 1-interesting polygon and appending 1-interesting polygons to its rim, side by side. You can see the 1-, 2-, 3- and 4-interesting polygons in the picture below.
Example
For n = 2, the output should be
solution(n) = 5;
For n = 3, the output should be
solution(n) = 13.
Input/Output
[execution time limit] 3 seconds (java)
[input] integer n
Guaranteed constraints:
1 ≤ n < 104.
[output] integer
The area of the n-interesting polygon.
int solution(int n) {
int sum = 1;
for(int i=0; i<n; i++){
sum += 4 * i;
}
return sum;
}