POJ 1276 Cash Machine

#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string>
#include<string.h>
#include<math.h>
#include<limits.h>
#include<time.h>
#include<stdlib.h>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<vector>
#define LL long long

using namespace std;

bool dp[100005];
int used[100005];
struct node
{
    int val, num;
}money[15];
int main()
{
    int n, m;
    while(~scanf("%d%d", &m, &n))
    {
        memset(dp, 0, sizeof dp);
        int ans = 0;
        for(int i = 1; i <= n; i++)
            scanf("%d%d", &money[i].num, &money[i].val);
        dp[0] = true;
        for(int i = 1; i <= n; i++)
        {
            memset(used, 0, sizeof used);
            for(int j = 1; j <= m; j++)
            {
                if(!dp[j] && j >= money[i].val && dp[j - money[i].val] && used[j - money[i].val] < money[i].num)
                {
                    ans = max(ans, j);
                    dp[j] = true;
                    used[j] = used[j - money[i].val] + 1;
                }
            }
        }
        printf("%d\n", ans);
    }
    return 0;
}