//

 //by coolxxx

 ////<bits/stdc++.h>

 #include<iostream>

 #include<algorithm>

 #include<string>

 #include<iomanip>

 #include<memory.h>

 #include<time.h>

 #include<stdio.h>

 #include<stdlib.h>

 #include<string.h>

 //#include<stdbool.h>

 #include<math.h>

 #define min(a,b) ((a)<(b)?(a):(b))

 #define max(a,b) ((a)>(b)?(a):(b))

 #define abs(a) ((a)>0?(a):(-(a)))

 #define lowbit(a) (a&(-a))

 #define sqr(a) ((a)*(a))

 #define swap(a,b) ((a)^=(b),(b)^=(a),(a)^=(b))

 #define mem(a,b) memset(a,b,sizeof(a))

 #define eps (1e-8)

 #define J 10

 #define MAX 0x7f7f7f7f

 #define PI 3.14159265358979323

 #define N 204

 #define M 5004

 #define K 54

 using namespace std;

 typedef long long LL;

 int cas,cass;

 int n,m,lll,ans;

 int v[N],c[N],t[K<<];

 int f[M][K];

 void merge(int a[],int b[],int c)

 {

     int i,j,k;

     for(i=,j=,k=;i+j<=cas+;)

     {

         if(a[i]>b[j]+c)t[++k]=a[i++];

         else t[++k]=b[j++]+c;

     }

     while(i<=cas)t[++k]=a[i++];

     while(j<=cas)t[++k]=b[j++]+c;

     for(i=;i<=cas;i++)a[i]=t[i];

 }

 int main()

 {

     #ifndef ONLINE_JUDGE

 //    freopen("1.txt","r",stdin);

 //    freopen("2.txt","w",stdout);

     #endif

     int i,j;

 //    for(scanf("%d",&cas);cas;cas--)

 //    for(scanf("%d",&cas),cass=1;cass<=cas;cass++)

 //    while(~scanf("%s",s))

     while(~scanf("%d",&cas))

     {

         mem(f,-0x7f);mem(t,-0x7f);ans=;

         scanf("%d%d",&m,&n);

         for(i=;i<=n;i++)

         {

             scanf("%d%d",&v[i],&c[i]);

         }

         f[][]=;

         for(i=;i<=n;i++)

         {

             for(j=m;j>=v[i];j--)

             {

                 merge(f[j],f[j-v[i]],c[i]);

             }

         }

         for(i=;i<=cas && f[m][i]>;i++)ans+=f[m][i];

         printf("%d\n",ans);

     }

     return ;

 }

 /*

 //

 //

 */