City X consists of n vertical and n horizontal infinite roads, forming n × n intersections. Roads (both vertical and horizontal) are numbered from 1 to n, and the intersections are indicated by the numbers of the roads that form them.

Sand roads have long been recognized out of date, so the decision was made to asphalt them. To do this, a team of workers was hired and a schedule of work was made, according to which the intersections should be asphalted.

Road repairs are planned for n² days. On the i-th day of the team arrives at the i-th intersection in the list and if none of the two roads that form the intersection were already asphalted they asphalt both roads. Otherwise, the team leaves the intersection, without doing anything with the roads.

According to the schedule of road works tell in which days at least one road will be asphalted.

The first line contains integer n (1 ≤ n ≤ 50) — the number of vertical and horizontal roads in the city.

Next n² lines contain the order of intersections in the schedule. The i-th of them contains two numbers h_i, v_i (1 ≤ h_i, v_i ≤ n), separated by a space, and meaning that the intersection that goes i-th in the timetable is at the intersection of the h_i-th horizontal and v_i-th vertical roads. It is guaranteed that all the intersections in the timetable are distinct.

In the single line print the numbers of the days when road works will be in progress in ascending order. The days are numbered starting from 1.

In the sample the brigade acts like that:

1. On the first day the brigade comes to the intersection of the 1-st horizontal and the 1-st vertical road. As none of them has been asphalted, the workers asphalt the 1-st vertical and the 1-st horizontal road;
2. On the second day the brigade of the workers comes to the intersection of the 1-st horizontal and the 2-nd vertical road. The 2-nd vertical road hasn't been asphalted, but as the 1-st horizontal road has been asphalted on the first day, the workers leave and do not asphalt anything;
3. On the third day the brigade of the workers come to the intersection of the 2-nd horizontal and the 1-st vertical road. The 2-nd horizontal road hasn't been asphalted but as the 1-st vertical road has been asphalted on the first day, the workers leave and do not asphalt anything;
4. On the fourth day the brigade come to the intersection formed by the intersection of the 2-nd horizontal and 2-nd vertical road. As none of them has been asphalted, the workers asphalt the 2-nd vertical and the 2-nd horizontal road.

题目意思：有n条横向的路和n条纵向的路，交叉得到n*n个路口，要修理路到某个路口，只有当形成这个路口的两条路都没有被修过的时候，这两条路才会被修，问那一天修过路。

解题思路：。。。。。。要什么思路分明是水题，可以我看不懂英语啊，英语是不可能看懂的，这辈子都不可能了（还是好好学吧，捂脸）

上代码：

 #include<stdio.h>

 #include<string.h>

 int main()

 {

    int n,x,y,k,i;

    int a[],s1[],s2[];

    scanf("%d",&n);

    k=;

    memset(s1,,sizeof(s1));

    memset(s2,,sizeof(s2));

    for(i=;i<=n*n;i++)

    {

        scanf("%d%d",&x,&y);

        if(s1[x]==&&s2[y]==)

         {

             s1[x]=;

             s2[y]=;

             a[k++]=i;

         }

    }

    for(i=;i<k;i++)

    {

        printf("%d ",a[i]);

    }

    printf("\n");

    return ;

 }