#include <bits/stdc++.h>
using namespace std;
int f[10005][10005];
struct n
{
	int w;
	int c;
}a[100005];
int main()
{
	int time,count;
	cin>>time>>count;
	for(int i=1;i<=count;i++)
	{
		cin>>a[i].w>>a[i].c;
	}
	for(int i=1;i<=count;i++)
	{
		for(int j=time;j>0;j--)
		{
			if(a[i].w<=time)
			{
				f[i][j]=max(f[i-1][j],f[i-1][j-a[i].w]+a[i].c);
			}
			else
			{
				f[i][j]=f[i-1][j];
			}
		}
	}
	cout<<f[count][time];
	return 0;
}