백준 13305

package baekjoon.그리디;

import java.util.*;
import java.io.*;

class Main13305 {

   public static void main(String[] args) throws Exception {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st;
      int N = Integer.parseInt(br.readLine());
      st = new StringTokenizer(br.readLine());
      int[] d = new int[N];
      int[] p = new int[N + 1];
      for (int i = 1; i < N; i++) {
         d[i] = Integer.parseInt(st.nextToken());
      }
      st = new StringTokenizer(br.readLine());
      for (int i = 1; i <= N; i++) {
         p[i] = Integer.parseInt(st.nextToken());
      }

      long ans = 0;
      int min = Integer.MAX_VALUE;
      for (int i = 1; i < N; i++) {
         min = Math.min(min, p[i]);
         ans += (long)min * d[i];
      }

      System.out.println(ans);

   }
}