C.cpp

//#pragma GCC optimize "trapv"
#pragma GCC optimize("Ofast")
#pragma GCC optimize("O3", "unroll-loops")
#pragma GCC target("avx,avx2,fma")
#include<bits/stdc++.h>
#define ll long long int
#define fab(a,b,i) for(int i=a;i<b;i++)
#define pb push_back
#define db double
#define mp make_pair
#define endl "\n"
#define f first
#define se second
#define all(x) x.begin(),x.end()
#define MOD 1000000007
#define vll vector<ll>
#define vi vector<int>
#define pii pair<int,int>
#define pll pair<ll,ll>
#define quick ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)

using namespace std;

ll add(ll x, ll y) {ll res = x + y; return (res >= MOD ? res - MOD : res);}
ll mul(ll x, ll y) {ll res = x * y; return (res >= MOD ? res % MOD : res);}
ll sub(ll x, ll y) {ll res = x - y; return (res < 0 ? res + MOD : res);}
ll power(ll x, ll y) {ll res = 1; x %= MOD; while (y) {if (y & 1)res = mul(res, x); y >>= 1; x = mul(x, x);} return res;}
ll mod_inv(ll x) {return power(x, MOD - 2);}
ll lcm(ll x, ll y) { ll res = x / __gcd(x, y); return (res * y);}


int main()
{	quick;
#ifndef ONLINE_JUDGE
	freopen("D:/sublime/input.txt", "r", stdin);
	freopen("D:/sublime/output.txt", "w", stdout);
#endif
	int n;
	cin >> n;
	ll a[n];
	fab(0, n, i)
	{
		cin >> a[i];
	}

	stack<int> s;
	vector<int> l(n), r(n);
	for ( int i = 0; i < n; i++)
	{
		while (s.size() and a[s.top()] >= a[i])
		{
			s.pop();

		}
		if (s.empty())
		{
			l[i] = -1;
		}
		else
			l[i] = s.top();

		s.push(i);
	}

	while (!s.empty())
		s.pop();
	for ( int i = n - 1; i >= 0; i--)
	{
		while (s.size() and a[s.top()] >= a[i])
		{
			s.pop();

		}
		if (s.empty())
		{
			r[i] = n ;
		}
		else
			r[i] = s.top();

		s.push(i);

	}
	ll ans = 0;
	fab(0, n, i)
	{
		ans = max(a[i] * (r[i] - l[i] - 1), ans);

	}
	cout << ans << endl;

	cerr << "time taken : " << (float)clock() / CLOCKS_PER_SEC << " secs" << endl;
	return 0;
}