#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main(void)
{
    ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    ll s,n,d;
    cin>>s>>n>>d;
    ll w[d+1]={0},v[d+1]={0};
    ll x=s;
    ll ans=0;
    for(ll i=1;i<=d;i++)
        cin>>w[i]>>v[i];
    ll f[100*x]={0};
    ll pre=0;
    for(ll i=1;i<=n;i++)
    {
        for(ll j=1;j<=d;j++)
        {
            ll d;
            if(w[j]>pre)
                d=w[j];
            else
                d=pre;
            for(ll q=d;q<=s;q++)
            {
                f[q]=max(f[q],f[q-w[j]]+v[j]);
            }
        }
        pre=s;
        s=s+f[s];
    }
    cout<<s;
}