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