#include<bits/stdc++.h>
using namespace std;
int n,k,a[100000],b[100000],dp[10000]; 

int main()
{
    cin>>n>>k;
    for(int i=1;i<=k;i++)cin>>a[i]>>b[i];
    for(int i=1;i<=k;i++)
    {
        for(int j=a[i];j<=n;j++)
        
        dp[j]=max(dp[j],dp[j-a[i]]+b[i]);
    }
    cout<<dp[n];
    return 0;
}

#include <iostream>
using namespace std;

int main()
{
int n, m, i, x;
int f[10010] = {0};
int w[10010] = {0}, u[10010] = {0};
cin >> n >> m;
for (i = 0; i < m; ++i)
cin >> w[i] >> u[i];
f[0] = 0;
for (i = 0; i < m; ++i)
for (x = w[i]; x <= n; ++x)
if (f[x - w[i]] + u[i] > f[x])
f[x] = f[x - w[i]] + u[i];
cout << f[n] << endl;
return 0;
}