#include <bits/stdc++.h>
#define qqbb ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
#define all(x) (x).begin(), (x).end()
#define int long long
#define endl '\n'
#define lb(x) x & -x
#define AA cerr<<"AA"<<endl;
using namespace std;
typedef pair<int, int> pii;
const int inf = 0x3f3f3f3f;

const int N = 2e5 + 10, M = 4e5 + 10;

void solve(){
    int n,m;cin>>n>>m;
    for(int i=1;i<=m;i++){
        int u,v;cin>>u>>v;
    }
    cout<<(n+m)/2;
}

signed main(){
    qqbb;
//	cout<<fixed<<setprecision(0);
    int Test=1;
//	cin>>Test;
    while(Test--){
        solve();
    }
    return 0;
}