HDU 5527 Too Rich

#include<cstdio>
#include<iostream>
#include<cmath>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<stack>
#include<string>
#include<sstream>
#include<cstring>
#include<algorithm>
using namespace std;
typedef long long ll;
int f[15]={0,1,5,10,20,50,100,200,500,1000,2000};
ll s[15];
int a[15];
int ans;
void dfs(int now,int i,int cnt)
{
    if (now<0) return;
    if (i==0)
    {
        if (now==0)
            ans=max(ans,cnt);
        return;
    }
    ll t=max(now-s[i-1],0LL);
    int num=t/f[i];
    if (t%f[i])
        num++;
    if (num<=a[i])
        dfs(now-num*f[i],i-1,cnt+num);
    num++;
    if (num<=a[i])
        dfs(now-num*f[i],i-1,cnt+num);
}
int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        int p;
        scanf("%d",&p);
        s[0]=0;
        for(int i=1;i<=10;i++)
        {
            scanf("%d",&a[i]);
            s[i]=s[i-1]+1LL*a[i]*f[i];
        }
        ans=-1;
        dfs(p,10,0);
        printf("%d\n",ans);
    }
    return 0;
}