C :

#include<stdio.h>
int dp[30001], v[26], w[26];
int max(int a,int b)
{
	if(a>b)
		return a;
	else
		return b;
}
int main()
{
	int N, m,i,j;
	scanf("%d%d",&N,&m);
    for(i=0;i<m;i++)
        scanf("%d%d",&v[i],&w[i]);
    dp[0]=0;
    for(i=0;i<m;i++)
        for(j=N;j>=v[i];j--)
            dp[j] = max(dp[j],dp[j-v[i]]+v[i]*w[i]);
    printf("%d\n",dp[N]);
	return 0;
}

C++ :

#include<iostream>
#include<algorithm>
#include<cstring>
#include<ctime>
#include<cmath>
#include<string>
#include<cstdio>
using namespace std;

int V, m, res = 0;
struct node{
    int v, w;
}P[30];

void dfs(int k, int v, int r)
{
    if(r > res) res = r;
    if(k == m + 1) return;
    dfs(k + 1, v, r);
    if(v > P[k].v) dfs(k + 1, v - P[k].v, r + P[k].w);
}

int main()
{
    cin>>V>>m;
    for(int i = 1; i <= m; ++i)
    {
        cin>>P[i].v>>P[i].w;
        P[i].w *= P[i].v;
    }
    dfs(0, V, 0);
    cout<<res<<endl;
    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.