#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N=1e6+10,inf=2147483647;
int cnt,n,ans;
struct node{
	int income,outcome;
	double value;
	bool operator < (const node& other) const{return value<other.value;}
} a[N];
signed main(){
//	ios::sync_with_stdio(0);
//	cin.tie(0);cout.tie(0);
	cin>>cnt>>n;
	for(int i=1;i<=n;++i){
		cin>>a[i].income>>a[i].outcome;
		a[i].value=a[i].income/a[i].outcome;
	}
	sort(a+1,a+n+1);
	for(int i=1;i<=n;++i){
//		cout<<i<<" "<<a[i].income<<","<<a[i].outcome<<"\n";
		while(cnt>=a[i].income){
			int x=cnt/a[i].income;
//			cout<<cnt<<" "<<x<<" "<<cnt-x*(a[i].income-a[i].outcome)<<"\n";
			ans+=x;
			cnt-=x*(a[i].income-a[i].outcome);
		}
//		cout<<"\n";
	}
	cout<<ans;
	return 0;
}