HDU-6501 Problem B. Memory Banks

#include <bits/stdc++.h>
#define _for(i,a,b) for(int i = (a);i < (b);i ++)
const int maxn = 100000 + 10;
const int mod=1000000007;
using namespace std;
typedef long long ll;

ll station[maxn];
ll qa(ll a,ll b)
{
    ll ans=0;
    while(b)
    {
        if(b&1)ans=(ans+a)%mod;
        a=(a+a)%mod;
        b>>=1;
    }
    return ans;
}
int main()
{
    ll liusi[70];
    while(~scanf("%lld",&liusi[0]))
    {
        _for(i,1,60)
            scanf("%lld",&liusi[i]);
        
        int n;
        scanf("%d",&n);
        _for(i,0,n)
        scanf("%lld",&station[i]);

        sort(station,station+n,greater<ll>());
        int flag = 0;
        for(int i = 0;i < n;i ++)
        {
            int j;
            for(j = 59;j >= 0;j --)
            {
                if(!liusi[j])
                    continue;
                ll a = ((ll)1<<j);
                if(a>station[i])
                    continue;
                
                ll b = station[i]/a;
                if(b>=liusi[j])
                {
                    station[i] -= liusi[j]*a;
                    liusi[j] = 0;
                }
                else
                {
                    station[i] -= b*a;
                    liusi[j] -= b;
                }
            }
            if(station[i])
            {
                flag = 1;
                break;
            }
        }
        if(flag)
        {
            printf("-1
");
            continue;
        }
        
        ll rnt = 0;
        for(int i = 59; i >= 0; i --)
        {
            if(liusi[i])
                rnt = (rnt + qa(liusi[i],1LL<<i)) % mod;
        }
        printf("%lld
",rnt);
    }
    return 0;
}