codeforces 38A Army_codeforce 38a army-优快云博客

本文链接：https://blog.youkuaiyun.com/zhang__liuchen/article/details/80142349

这篇博客介绍了Berland军队的军衔系统，每个军衔之间的晋升需要一定年限。Vasya刚达到军衔a，他的目标是达到军衔b。文章计算了Vasya实现这个梦想所需额外服役的年数。

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The Berland Armed Forces System consists of n ranks that are numbered using natural numbers from 1 to n, where 1 is the lowest rank and n is the highest rank.

One needs exactly di years to rise from rank i to rank i + 1. Reaching a certain rank i having not reached all the previous i - 1 ranks is impossible.

Vasya has just reached a new rank of a, but he dreams of holding the rank of b. Find for how many more years Vasya should serve in the army until he can finally realize his dream.

Input

The first input line contains an integer n (2 ≤ n ≤ 100). The second line contains n - 1 integers di (1 ≤ di ≤ 100). The third input line contains two integers a and b (1 ≤ a < b ≤ n). The numbers on the lines are space-separated.

Output

Print the single number which is the number of years that Vasya needs to rise from rank a to rank b.

   Examples
 
     input 
    
      Copy
    
3
5 6
1 2

     output 
    
      Copy
    
5

     input 
    
      Copy
    
3
5 6
1 3

     output 
    
      Copy
    
11

水题，翻译过去就能做出来了吧

/* ***********************************************
Author :zhangxiaofeng
Email :154704230@qq.com
Created Time :2018年04月29日 星期日 10时58分50秒
File Name :main.cpp
************************************************ */

#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;

int main()
{
// freopen("in.txt","r",stdin);
 //freopen("out.txt","w",stdout);
 int n;
 cin>>n;
 int a[110];
 for(int i=1;i<n;i++)
 {
	 cin>>a[i];
 }
 int x,y;
 cin>>x>>y;
 int ans=0;
 for(int i=x;i<y;i++)
 {
	 ans+=a[i];
 }
 cout<<ans<<endl;
 return 0;
}