/*
用1742的方法,秒杀
*/
// include file
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <cctype>
#include <ctime>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <bitset>
#include <algorithm>
#include <string>
#include <vector>
#include <queue>
#include <set>
#include <list>
#include <functional>
using namespace std;
// typedef
typedef long long LL;
typedef unsigned long long ULL;
//
#define read freopen("in.txt","r",stdin)
#define write freopen("out.txt","w",stdout)
#define FORi(a,b,c) for(int i=(a);i<(b);i+=c)
#define FORj(a,b,c) for(int j=(a);j<(b);j+=c)
#define FORk(a,b,c) for(int k=(a);k<(b);k+=c)
#define FORp(a,b,c) for(int p=(a);p<(b);p+=c)
#define FORii(a,b,c) for(int ii=(a);ii<(b);ii+=c)
#define FORjj(a,b,c) for(int jj=(a);jj<(b);jj+=c)
#define FORkk(a,b,c) for(int kk=(a);kk<(b);kk+=c)
#define FF(i,a) for(int i=0;i<(a);i++)
#define FFD(i,a) for(int i=(a)-1;i>=0;i--)
#define Z(a) (a<<1)
#define Y(a) (a>>1)
const double eps = 1e-6;
const double INFf = 1e100;
const int INFi = 2000000000;
const LL INFll = (LL)1<<62;
const double Pi = acos(-1.0);
template<class T> inline T sqr(T a){return a*a;}
template<class T> inline T TMAX(T x,T y)
{
if(x>y) return x;
return y;
}
template<class T> inline T TMIN(T x,T y)
{
if(x<y) return x;
return y;
}
template<class T> inline void SWAP(T &x,T &y)
{
T t = x;
x = y;
y = t;
}
template<class T> inline T MMAX(T x,T y,T z)
{
return TMAX(TMAX(x,y),z);
}
template<class T> inline T MMIN(T x,T y,T z)
{
return TMIN(TMIN(x,y),z);
}
// code begin
int M,N;
bool DP[100010];
int V[11];
int C[11];
int cnt[100010][2];
int main()
{
read;
write;
while(scanf("%d %d",&M,&N)==2)
{
FORi(1,N+1,1)
{
scanf("%d %d",C+i,V+i);
}
memset(DP,0,sizeof(DP));
DP[0] = true;
FORi(1,N+1,1)
{
FORj(0,M+1,1)
{
if(j+V[i]>M) break;
if(DP[j] && !DP[j+V[i]])
{
if(cnt[j][0]!=i)
{
cnt[j][0] = i;
cnt[j][1] = 0;
}
if( cnt[j][1]+1<=C[i] )
{
DP[j+V[i]] = true;
cnt[j+V[i]][1] = cnt[j][1]+1;
cnt[j+V[i]][0] = i;
}
}
}
}
int ans = 0;
for(int i=M;i>=0;i--)
if(DP[i])
{
ans = i;
break;
}
printf("%d\n",ans);
}
return 0;
}