BZOJ 4052 Cerc2013 Magical GCD

[code]#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define M 100100
using namespace std;
int n;
long long a[M],ans;
pair<int,long long> stack[20],_stack[20];
int top;
void Initialize()
{
    ans=0;
    top=0;
}
int main()
{
    int T,i,j;
    for(cin>>T;T;T--)
    {
        Initialize();
        scanf("%d",&n);
        for(i=1;i<=n;i++)
        {
            scanf("%lld",&a[i]);
            stack[++top]=make_pair(i,0);
            for(j=1;j<=top;j++)
                stack[j].second=__gcd(stack[j].second,a[i]);
            int temp=0;
            for(j=1;j<=top;j++)
                if(j==1||stack[j].second!=stack[j-1].second)
                    _stack[++temp]=stack[j];
            memcpy(stack,_stack,sizeof stack);
            top=temp;
            for(j=1;j<=top;j++)
                ans=max(ans,stack[j].second*(i-stack[j].first+1));
        }
        printf("%lld\n",ans);
    }
    return 0;
}