A. Points in Segments

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本文介绍了一个算法问题：给定一系列区间，如何找出这些区间未覆盖的所有整数点。通过使用C++实现的示例代码，展示了如何初始化数组、标记区间内的点，并最终找出所有未被区间覆盖的点。

A. Points in Segments

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

You are given a set of nn segments on the axis OxOx, each segment has integer endpoints between 11 and mm inclusive. Segments may intersect, overlap or even coincide with each other. Each segment is characterized by two integers lili and riri (1≤li≤ri≤m1≤li≤ri≤m) — coordinates of the left and of the right endpoints.

Consider all integer points between 11 and mm inclusive. Your task is to print all such points that don't belong to any segment. The point xxbelongs to the segment [l;r][l;r] if and only if l≤x≤rl≤x≤r.

Input

The first line of the input contains two integers nn and mm (1≤n,m≤1001≤n,m≤100) — the number of segments and the upper bound for coordinates.

The next nn lines contain two integers each lili and riri (1≤li≤ri≤m1≤li≤ri≤m) — the endpoints of the ii-th segment. Segments may intersect, overlap or even coincide with each other. Note, it is possible that li=rili=ri, i.e. a segment can degenerate to a point.

Output

In the first line print one integer kk — the number of points that don't belong to any segment.

In the second line print exactly kk integers in any order — the points that don't belong to any segment. All points you print should be distinct.

If there are no such points at all, print a single integer 00 in the first line and either leave the second line empty or do not print it at all.

Examples

input

Copy

output

Copy

2
3 4

input

Copy

1 7
1 7

output

Copy

Note

In the first example the point 11 belongs to the second segment, the point 22 belongs to the first and the second segments and the point 55belongs to the third segment. The points 33 and 44 do not belong to any segment.

In the second example all the points from 11 to 77 belong to the first segment.

代码：

#include <iostream>
#include <cstdio>

using namespace std;

int main()
{
    int a[105];
    fill(a,a+105,0);
    int n,m;
    scanf("%d%d",&n,&m);
    for(int i=0;i<n;++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        fill(a+x,a+y+1,1);
    }
    int ans=0;
    for(int i=1;i<=m;++i)
    {
        if(a[i]==0) ans++;
    }
    cout<<ans<<endl;
    for(int i=1;i<=m;++i)
    {
        if(a[i]==0) cout<<i<<" ";
    }
    return 0;
}