CodeForces 558A Lala Land and Apple Trees

A. Lala Land and Apple Trees

time limit per test
1 second

memory limit per test
256 megabytes

input
standard input

output
standard output

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 xi and
has ai 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 xi, ai ( - 105 ≤ xi ≤ 105, xi ≠ 0, 1 ≤ ai ≤ 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.

题意：n棵苹果树在x轴上排成一排，每棵苹果树有一个坐标值（均不为0）和苹果数量。现在某人从0开始任意选择一个方向走，每遇到一颗新的苹果树就摘下所有苹果，然后掉转方向直到遇到下一颗之前没遇到过的苹果树然后再摘下所有苹果，如此往复直到再也遇不到新的苹果树。问最多能摘下多少个苹果。
思路，水题。

#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;
struct node
{
int a,b;
}t[110];
bool cmp(node x,node y)
{
return x.a<y.a;
}
int main()
{
int a[110],b[110],i,n,sum1,sum2,sum;
while(scanf("%d",&n)!=EOF)
{
int m=1000;
sum1=0;
sum2=0;
for(i=1;i<=n;i++)
scanf("%d%d",&t[i].a,&t[i].b);
sort(t+1,t+n+1,cmp);
for(i=1;i<=n;i++)
{
if(t[i].a>0)
{
m=i;
break;
}
}
if(m==1)
printf("%d\n",t[1].b);
else if(m==1000)
{
printf("%d\n",t
.b);
}
else
{
int left=m-1;
int right=n-m+1;
if(left>right)
{
for(i=m;i<=n;i++)
sum1+=t[i].b;
for(i=m-1;i>=m-right-1;i--)
sum2+=t[i].b;
sum=sum1+sum2;
printf("%d\n",sum);
}
else if(left<right)
{
for(i=m;i<=m+left;i++)
sum1+=t[i].b;
for(i=m-1;i>0;i--)
sum2+=t[i].b;
sum=sum1+sum2;
printf("%d\n",sum);
}
else if(left==right)
{
for(i=1;i<=n;i++)
sum1+=t[i].b;
printf("%d\n",sum1);
}
}
}
return 0;
}