【CodeForces 1366B--- Shuffle】

题目来源：点击进入【CodeForces 1366B— Shuffle】

Description

You are given an array consisting of n integers a1, a2, …, an. Initially ax=1, all other elements are equal to 0.

You have to perform m operations. During the i-th operation, you choose two indices c and d such that li≤c,d≤ri, and swap ac and ad.

Calculate the number of indices k such that it is possible to choose the operations so that ak=1 in the end.

Input

The first line contains a single integer t (1≤t≤100) — the number of test cases. Then the description of t testcases follow.

The first line of each test case contains three integers n, x and m (1≤n≤109; 1≤m≤100; 1≤x≤n).

Each of next m lines contains the descriptions of the operations; the i-th line contains two integers li and ri (1≤li≤ri≤n).

Output

For each test case print one integer — the number of indices k such that it is possible to choose the operations so that ak=1 in the end.

Sample Input

3
6 4 3
1 6
2 3
5 5
4 1 2
2 4
1 2
3 3 2
2 3
1 2

Sample Output

6
2
3

Note

In the first test case, it is possible to achieve ak=1 for every k. To do so, you may use the following operations:

• swap ak and a4;
• swap a2 and a2;
• swap a5 and a5.

In the second test case, only k=1 and k=2 are possible answers. To achieve a1=1, you have to swap a1 and a1 during the second operation. To achieve a2=1, you have to swap a1 and a2 during the second operation.

AC代码(C++)：

#include 
#include 
#define SIS std::ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define endl '\n'
using namespace std;
typedef long long ll;
const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const int MAXN = 1e5+5;

int main(){
    SIS;
    int t,n,x,m,a,b,l,r;
    cin >> t;
    while(t--){
        cin >> n >> x >> m;
        l=r=x;
        while(m--){
            cin >> a >> b;
            if(b<l || a>r) continue;
            l=min(l,a);
            r=max(r,b);
        }
        cout << r-l+1 << endl;
    }
    return 0;
}