C++ :

#include <iostream>   
#include <limits.h>   
#include <algorithm>   
using namespace std;   
#define F(i,j,k) for (int i=j;i<=k;i++)   
int n,m;   
int w[50],v[50];   
int f[30000];   
int main()   
{   
    cin>>n>>m;   
    F(i,1,m)   
    {   
        cin>>v[i]>>w[i];   
    }   
    F(i,1,m)   
    {   
        for (int j=n;j>=v[i];j--)   
        {   
            f[j]=max(f[j-v[i]]+v[i]*w[i],f[j]);   
        }   
    }   
    cout<<f[n];   
    return 0;   
}  

Pascal :

var n,m,w,c,i,j:longint;
   f:array[0..100000]of longint;
begin
  readln(n,m);
  for i:=1 to m do begin
    readln(w,c);
    c:=c*w;
    for j:= n downto w do
    if f[j-w]+c>f[j] then f[j]:=f[j-w]+c;
  end;
  for i:=2 to n do
  if f[i]>f[1] then f[1]:=f[i];
  writeln(f[1]);
end.