#include<algorithm>
#include<string>
#include<stdio.h>
#include<map>
#include<iostream>
#include<vector>
#include<iomanip>
#include<random>
#include<cmath>
#include<set>
using namespace std;
int m;vector<int>kk(10000000); long long all,cnt;
void input(long long a,long long b) {
	kk[++cnt] = a;
	all += a;
	for (int i = 1; i <= b; i++) {
		long long  a1, b1;
		cin >> a1 >> b1;
		input(a1, b1);
	}
}
int main() {
	cin >> m;
	long long a, b;
	cin >> a >> b;
	input(a, b);
	long long ans = all / m + 1;
	cout << ans<<endl;
	return 0;
}