import java.util.ArrayList;
import java.util.Scanner;

/**
 *
 * @author student
 */
public class MadeDriver {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        float result = 0;
        int ans=0;
        int count = sc.nextInt();
        ArrayList<Integer> inputs = new ArrayList<Integer>();
        inputs.add(0);
        for (int i = 0; i < count; i++) {
            inputs.add(sc.nextInt());
        }
        for (int i = 0; i < count; i++) {
            int firstDirection = inputs.get(i);
            int secondDirection = inputs.get(i + 1);
            int diff = secondDirection - firstDirection;
            //case up and simple
            float cal = 0.0f;
            if (diff >= 0) {
                diff = Math.abs(diff);
                cal = ((diff * diff) + 2);
                ans += cal*60;
            } else { //case down
                diff = Math.abs(diff);
                cal = (float)(1.0f / diff);
                ans+=(int)(60*cal);
            }
            //System.out.println("diff "+diff+ ",cal = "+cal);
            result+=cal;
        }
        //System.out.println(String.format("%.02f, value %d", result, ans));
        System.out.println(String.format("%d", ans));
    }
}