2020 BIT冬训-C++STL H - Lala Land and Apple Trees CodeForces - 558A

Problem Description

Amr lives in Lala Land. Lala Land is a very beautiful country that is located on a coordinate line.

Lala Land is famous with its apple trees growing everywhere.Lala Land has exactly n apple trees.

Tree number i is located in a position x_i and has a_i apples growing on it. Amr wants to collect apples

from the apple trees. Amr currently stands in x = 0 position. At the beginning, he can choose whether

to go right or left. He'll continue in his direction until he meets an apple tree he didn't visit before. He'll

take all of its apples and then reverse his direction, continue walking in this direction until he meets

another apple tree he didn't visit before and so on. In the other words, Amr reverses his direction when

visiting each new apple tree. Amr will stop collecting apples when there are no more trees he didn't visit

in the direction he is facing.What is the maximum number of apples he can collect?

 

Input

The first line contains one number n (1 ≤ n ≤ 100), the number of apple trees in Lala Land.

The following n lines contains two integers each x_i, a_i ( - 10⁵ ≤ x_i ≤ 10⁵, x_i ≠ 0, 1 ≤ a_i ≤ 10⁵),

representing the position of the i-th tree and number of apples on it.

It's guaranteed that there is at most one apple tree at each coordinate.

It's guaranteed that no tree grows in point 0.

 

Output

Output the maximum number of apples Amr can collect.

 

Examples

Input

2
-1 5
1 5

Output

10

Input

3
-2 2
1 4
-1 3

Output

9

Input

3
1 9
3 5
7 10

Output

9

Note

In the first sample test it doesn't matter if Amr chose at first to go left or right. In both cases he'll get all the apples.

In the second sample test the optimal solution is to go left to x =  - 1, collect apples from there, then the direction will

be reversed, Amr has to go to x = 1, collect apples from there, then the direction will be reversed and Amr goes to the

final tree x =  - 2.In the third sample test the optimal solution is to go right to x = 1, collect apples from there, then the

direction will be reversed and Amr will not be able to collect anymore apples because there are no apple trees to his left.

本题的思路很简单。就是看正负轴上苹果树的数量。根据数量的关系狂暴写if即可

 

#include<stdio.h>
#include<algorithm>
using namespace std;
typedef pair<int,int> pii;
int n,z,f,ans;
pair<int,int>tree[105];
int cmp(const pii &a,const pii &b){
    return a.first<b.first; 
}
int main(){
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        scanf("%d%d",&tree[i].first,&tree[i].second);
        if(tree[i].first>0)
            z++;
        else if(tree[i].first<0)
            f++;         
    }
    sort(tree,tree+n,cmp);
    if(abs(z-f)<=1){
        for(int i=0;i<n;i++)
            ans+=tree[i].second;
    }else if(z>0&&f>0){
        int m=min(z,f);
        if(f<z){
            ans+=tree[f].second;
            for(int i= 0;i<m;i++){
                ans+=tree[f+i+1].second;
                ans+=tree[f-i-1].second;
            }
        }else{
            ans+=tree[f-1].second;
            for(int i= 0;i<m;i++){
                ans+=tree[f+i].second;
                ans+=tree[f-i-2].second;
            }
        }
    }else if(z==0){
        ans = tree[n-1].second;
    }
    else if(f==0){
        ans = tree[0].second;    
    }
    printf("%d",ans);
    
}