poj1276

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>

using namespace std;

int dp[100001];
int cash,N;
struct money
{
	int num;
	int value;
};

money moneys[10];

int main()
{
	while (scanf("%d%d",&cash,&N)!=EOF)
	{
		
		for (int i=0;i<N;++i)
		{
			scanf("%d%d",&moneys[i].num,&moneys[i].value);
		}
		memset(dp,0,sizeof(dp));
		int maxValue = 0;
		for (int i=0;i<N;++i)
		{
			money &m = moneys[i];
			if (m.num * m.value >=cash)//完全背包问题
			{
				for (int v=m.value;v<=cash;++v)
				{
					dp[v] = max(dp[v],dp[v-m.value] + m.value);
				}
				continue;
			}

			//多重背包问题
			int count = m.num;
			int k = 1;
			while(k<count)
			{
				int value = k * m.value;
				for (int v=cash;v >=value;--v)
				{
					dp[v] = max(dp[v],dp[v-value] +value);
				}
				count -=k;
				k = 2*k;
			}
			int value = count * m.value;
			for (int v=cash;v>=value;--v)
			{
				dp[v] = max(dp[v],dp[v-value] + value);
			}
		}
		cout<<dp[cash]<<endl;

	}
	return 0;
}