#include <bits/stdc++.h>
using namespace std;
#define A first
#define B second
#define MP make_pair
#define ms(a, x) memset(a, x, sizeof(a))
#define boost() ios_base::sync_with_stdio(false); cin.tie(NULL)
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<long long, long long> pll;
typedef pair<long double, long double> pld;
const int INF = 0x3f3f3f3f;
const double PI = acos(-1);
const int mxN=1e4+1e3+5;
int dp[505][mxN], l, n;
vector <pii> v;
ll solve(int pos, int range){
if(pos == n)
return 0;
if(dp[pos][range] != -1)
return dp[pos][range];
ll ret = solve(pos+1, range);
if(v[pos].B < range)
ret = max(ret, solve(pos+1, v[pos].B)+1);
return dp[pos][range]=ret;
}
int main(){
ms(dp, -1);
cin >> l >> n;
for(int i=0; i<n; i++){
int x, y;
cin >> x >> y;
v.push_back({x, l/y + x + (l/y % 2)});
}
sort(v.begin(), v.end());
cout << solve(0, mxN-5);
}
// 3 1 2 1 1
