p03894 CODE FESTIVAL 2016 Relay (Parallel) - Magician_33270
You have N cups and 1 ball.

The cups are arranged in a row, from left to right.

You turned down all the cups, then inserted the ball into the leftmost cup.

Then, you will perform the following Q operations:

* The i-th operation: swap the positions of the A_i-th and B_i-th cups from the left. If one of these cups contains the ball, the ball will also move.



Since you are a magician, you can cast a magic described below:

* Magic: When the ball is contained in the i-th cup from the left, teleport the ball into the adjacent cup (that is, the (i-1)-th or (i+1)-th cup, if they exist).



The magic can be cast before the first operation, between two operations, or after the last operation, but you are allowed to cast it at most once during the whole process.

Find the number of cups with a possibility of containing the ball after all the operations and possibly casting the magic.

Constraints

* 2 \leq N \leq 10^5
* 1 \leq Q \leq 10^5
* 1 \leq A_i < B_i \leq N

Input

The input is given from Standard Input in the following format:


N Q
A_1 B_1
A_2 B_2
:
A_Q B_Q


Output

Print the number of cups with a possibility of eventually containing the ball.

Examples

Input

10 3
1 3
2 4
4 5


Output

4


Input

20 3
1 7
8 20
1 19


Output

5
#include <bits/stdc++.h>
using namespace std;
#define int long long
#define ld long double
#define ll long long
#define P pair<int,int>
#define fi first
#define se second
#define rep(i,n) for(int i=0;i<n;i++)
#define all(v) v.begin(),v.end()
#define pb push_back
#define eb emplace_back
template<class T>void chmax(T &a,T b){if(a<b)a=b;}
template<class T>void chmin(T &a,T b){if(a>b)a=b;}
constexpr int INF=1000000000000000000;
constexpr int mod=1000000007;
constexpr double eps=1e-8;
const double pi=acos(-1);
int dx[]={0,1,0,-1},dy[]={1,0,-1,0};
int Random(int mi,int ma){
    random_device rnd;
    mt19937 mt(rnd());//32bit
    //[mi,ma]
    uniform_int_distribution<int>engine(mi,ma);
    return engine(mt);
}
int gcd(int a,int b){
    if(b==0)return a;
    return gcd(b,a%b);
}
int lcm(int a,int b){
    return a/gcd(a,b)*b;
}
bool prime(int a){
    if(a==1)return false;
    for(int i=2;i*i<=a;i++){
        if(a%i==0)return false;
    }
    return true;
}
int modpow(int a,int b){
    if(b==0)return 1;
    if(b%2)return modpow(a,b-1)*a%mod;
    int memo=modpow(a,b/2);
    return memo*memo%mod;
}
vector<int>kaijo,invkaijo;
void init_fact(int n){
    kaijo.resize(n+1);
    invkaijo.resize(n+1);
    kaijo[0]=1;
    for(int i=1;i<=n;i++){
        kaijo[i]=kaijo[i-1]*i;
        kaijo[i]%=mod;
    }
    rep(i,n+1)invkaijo[i]=modpow(kaijo[i],mod-2);
}
int comb(int a,int b){
    if(a<b)return 0;
    if(a<0||b<0)return 0;
    return kaijo[a]*modpow(kaijo[a-b],mod-2)%mod*modpow(kaijo[b],mod-2)%mod;
}
int inv(int x){
    x=modpow(x,mod-2);
    return x;
}
int n,q,pos=0,v[100010];
map<int,int>mp;
signed main(){
    cin.tie(0);ios::sync_with_stdio(false);
    cin>>n>>q;
    rep(i,n)v[i]=i;
    mp[0]=1,mp[1]=1;
    rep(i,q){
        int a,b;
        cin>>a>>b;
        a--,b--;
        if(a==pos){
            pos=b;
        }
        else if(b==pos){
            pos=a;
        }
        swap(v[a],v[b]);
        if(pos!=0)mp[v[pos-1]]++;
        if(pos+1!=n)mp[v[pos+1]]++;
    }
    cout<<mp.size()<<endl;
    return 0;
}