Codeforces 650A Watchmen

传送门

time limit per test　　3 seconds

memory limit per test　　256 megabytes

input　　standard input

output　　standard output

Watchmen are in a danger and Doctor Manhattan together with his friend Daniel Dreiberg should warn them as soon as possible. There are n watchmen on a plane, the i-th watchman is located at point (x_i, y_i).

They need to arrange a plan, but there are some difficulties on their way. As you know, Doctor Manhattan considers the distance between watchmen i and j to be |x_i - x_j| + |y_i - y_j|. Daniel, as an ordinary person, calculates the distance using the formula .

The success of the operation relies on the number of pairs (i, j) (1 ≤ i < j ≤ n), such that the distance between watchman i and watchmen j calculated by Doctor Manhattan is equal to the distance between them calculated by Daniel. You were asked to compute the number of such pairs.

Input

The first line of the input contains the single integer n (1 ≤ n ≤ 200 000) — the number of watchmen.

Each of the following n lines contains two integers x_i and y_i (|x_i|, |y_i| ≤ 10⁹).

Some positions may coincide.

Output

Print the number of pairs of watchmen such that the distance between them calculated by Doctor Manhattan is equal to the distance calculated by Daniel.

Examples

Input

3
1 1
7 5
1 5

Output

2

Input

6
0 0
0 1
0 2
-1 1
0 1
1 1

Output

11

Note

In the first sample, the distance between watchman 1 and watchman 2 is equal to |1 - 7| + |1 - 5| = 10 for Doctor Manhattan and for Daniel. For pairs (1, 1), (1, 5) and (7, 5), (1, 5) Doctor Manhattan and Daniel will calculate the same distances.

--------------------------------------------------------------------------------------

Solution

不难看出，

两点(x1,y1), (x2,y2)的曼哈顿距离=欧几里得距离<==> x1=x2或y1=y2

对于所有x与y坐标，统计在对应竖直线与水平线上的点的个数，再删除重合点造成的重复计数即可，当然也要统计重合点的数目。

Implementation

#include <bits/stdc++.h>
using namespace std;

typedef long long LL;

map<pair<int,int>,LL> m;
map<int,LL> cnt[2];


int main(){
    ios::sync_with_stdio(false);
    int n;
    cin>>n;
    for(int i=0; i<n; i++){
        int x, y;
        cin>>x>>y;
        cnt[0][x]++; cnt[1][y]++;
        m[{x,y}]++;
    }
    LL ans=0;
    for(int i=0; i<2; i++)
        for(auto it=cnt[i].begin(); it!=cnt[i].end(); it++){
            ans+=it->second*(it->second-1)/2;
        }
    for(auto it=m.begin(); it!=m.end(); it++)
        ans-=it->second*(it->second-1)/2;
    cout<<ans<<'
';
    return 0;
}

 用range-for还可将for-head写得更简洁些：

#include <bits/stdc++.h>
using namespace std;

typedef long long LL;

map<pair<int,int>,LL> m;
map<int,LL> cnt[2];


int main(){
    ios::sync_with_stdio(false);
    int n;
    cin>>n;
    for(int i=0; i<n; i++){
        int x, y;
        cin>>x>>y;
        cnt[0][x]++; cnt[1][y]++;
        m[{x,y}]++;
    }
    LL ans=0;
    for(int i=0; i<2; i++)
        for(auto it:cnt[i])
            ans+=it.second*(it.second-1)/2;
    for(auto it:m)
        ans-=it.second*(it.second-1)/2;
    cout<<ans<<'
';
    return 0;
}

 ---------------------------------------------------

记录这道题是为了复习STL containers。

基础不牢，地动山摇。