1 //#include <bits/stdc++.h>
 2 #include <iostream>
 3 #include <utility>
 4 #include <vector>
 5 #include <cstring>
 6 using namespace std;
 7 #define fst first
 8 #define scd second
 9 #define pb(x) push_back((x))
10 #define mkp(x,y) make_pair((x),(y))
11 #define ist(x) insert((x))
12 typedef long long ll;
13 typedef pair<int ,int > pii;
14 typedef pair<ll ,ll > pll;
15 typedef vector< int > vi;
16 ll gcd(ll a,ll b){ return b==0?a:gcd(b,a%b);}
17 ll qPow(ll a,ll b,ll mod){ ll ret=1ll;while(b){ if(b&1) ret=ret*a%mod;a=a*a%mod;b>>=1;} return ret; }
18
19 pii nD[13];
20 int dp[100000+5];
21 int nValue;
22
23 void ZeroOnePack(int cost , int weight){
24     for(int i=nValue;i>=cost;i--)
25         dp[i]=max(dp[i],dp[i-cost]+weight);
26 }
27
28 void CompletePack(int cost , int weight){
29     for(int i=cost;i<=nValue;++i)
30         dp[i]=max(dp[i],dp[i-cost]+weight);
31 }
32
33 void MultiplePack(int cost ,int weight,int amount){
34     if(cost*amount>=nValue) CompletePack(cost , weight);
35     else{
36         int k=1;
37         while(k<amount){
38             ZeroOnePack(k*cost,k*weight);
39             amount-=k;
40             k<<=1;
41         }
42         ZeroOnePack(amount*cost,amount*weight);
43     }
44 }
45
46 int main(){
47     int cash,N;
48     while(cin>>cash>>N){
49         nValue=cash;
50         memset(dp,0,sizeof(dp));
51         for(int i=0;i<N;++i)
52             cin>>nD[i].first>>nD[i].second;
53         for(int i=0;i<N;++i){
54             MultiplePack(nD[i].second,nD[i].second,nD[i].first);
55         }
56         cout<<dp[cash]<<endl;
57     }
58     return 0;
59 }