#include <iostream>
#include <string.h>
using namespace std;
int dp[105][1005], w[105],v[105],T,M,;
int max(int x,int y) { return x>y?x:y; }
int f(int x,int y)
{ int t;
if (dp[x][y]!=-1) return dp[x][y];
if ( x==M+1 || y==0 ) return dp[x][y]=0;
else
{ t=f(x+1,y);
if ( y>=w[x] ) dp[x][y]=max(t,f(x+1,y-w[x])+v[x] ); else dp[x][y]=t;
}
return dp[x][y] ;
}
int main()
{ int i,j;
cin>>T>>M;
for ( i=1; i<=M; i++) cin>>w[i]>>v[i];
memset(dp,-1,sizeof(dp));
f(1,T);
cout<<dp[1][T]<<endl;
return 0;
}