http://poj.org/problem?id=3494
https://blog.csdn.net/zuzhiang/article/details/78136417
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<stack>
using namespace std;
typedef long long ll;
ll read()
{
char ch=' ';
ll f=1;ll x=0;
while(ch<'0'||ch>'9')
{
if(ch=='-') f=-1;ch=getchar();
}
while(ch>='0'&&ch<='9')
{
x=x*10+ch-'0';ch=getchar();
}
return x*f;
}
const ll N=2100;
ll a[N];
ll l[N],r[N];
stack <ll> s;
void init()
{
while(!s.empty())
{
s.pop();
}
}
int main()
{
ll n,m;
ll i,j;
ll x;
while(scanf("%lld%lld",&n,&m)!=EOF)
{
ll ans=0;
memset(a,0,sizeof(a));
a[0]=-1;a[n+1]=-1;
for(i=1;i<=n;i++)
{
for(j=1;j<=m;j++)
{
x=read();
if(x==1) a[j]+=1;
else a[j]=0;
}
init();
for(j=1;j<=n+1;j++)
{
while(!s.empty()&&a[j]<a[s.top()])
{
r[s.top()]=j;
s.pop();
}
s.push(j);
}
init();
for(j=n;j>=0;j--)
{
while(!s.empty()&&a[j]<a[s.top()])
{
l[s.top()]=j;
s.pop();
}
s.push(j);
}
ll sum=0;
for(j=1;j<=n;j++)
{
sum=max(sum,(r[j]-1-l[j]-1+1)*a[j]);
}
ans=max(ans,sum);
}
cout<<ans<<endl;
}
return 0;
}