1 import java.util.Scanner;
2 // 1:无需package
3 // 2: 类名必须Main, 不可修改
4
5 public class Main {
6 public static void main(String[] args) {
7 Scanner sc = new Scanner(System.in);
8 int n = sc.nextInt();
9 int[] x = new int[n+1];
10 int[] a = new int[n+1];
11 int[] b = new int[n+1];
12 for(int i = 1;i<=n;i++){
13 x[i] = sc.nextInt();
14 }
15 for(int i = 1;i<n;i++){
16 a[i] = sc.nextInt();
17 b[i+1] = sc.nextInt();
18 }
19
20 double[][] dp = new double[n+1][2];
21 dp[1][0] = x[1];
22 dp[1][1] = x[1] + a[1]/0.7;
23
24
25 for(int i = 2;i <= n;i++){
26 if(a[i]>b[i]){
27 dp[i][1] = Math.min(dp[i-1][0] + x[i]-x[i-1] + a[i]/0.7, dp[i-1][1] + (a[i]-b[i])/0.7);
28 }else {
29 dp[i][1] = Math.min(dp[i-1][0] + x[i]-x[i-1] + a[i]/0.7,dp[i-1][1] + (b[i]-a[i]) /1.3);
30 }
31 dp[i][0] = Math.min(dp[i-1][1] +b[i]/1.3 ,dp[i-1][0]+x[i]-x[i-1]);
32
33 }
34
35
36 System.out.printf("%.2f",dp[n][0]);
37 //在此输入您的代码...
38 sc.close();
39 }
40 }
