Language: C++

#pragma GCC optimize("Ofast")

#include <bits/stdc++.h>

using namespace std;

typedef __int128_t ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<ld,ld> pdd;

#define X first
#define Y second

//#include <boost/unordered_map.hpp>
//using namespace boost;

/*
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> rbtree;
rbtree T;
*/

namespace io{
	const int L = (1 << 20) + 1;
	
	char buf[L], *S , *T, c;
	 
	char getchar() {
		if(__builtin_expect(S == T, 0)) {
			T = (S = buf) + fread(buf, 1, L, stdin);
			return (S == T ? EOF : *S++);
		}
		return *S++;
	}
	
	int inp() {
		int x = 0, f = 1; char ch;
		for(ch = getchar(); !isdigit(ch); ch = getchar())
			if(ch == '-') f = -1;
		for(; isdigit(ch); x = x * 10 + ch - '0', ch = getchar());
		return x * f;
	}
	
	unsigned inpu()
	{
		unsigned x = 0; char ch;
		for(ch = getchar(); !isdigit(ch); ch = getchar());
		for(; isdigit(ch); x = x * 10 + ch - '0', ch = getchar());
		return x;
	}
	
	ll inp_ll() {
		ll x = 0; int f = 1; char ch;
		for(ch = getchar(); !isdigit(ch); ch = getchar())
			if(ch == '-') f = -1;
		for(; isdigit(ch); x = x * 10 + ch - '0', ch = getchar());
		return x * f;
	}
	
	char B[25], *outs=B+20, *outr=B+20;
	template<class T>
	inline void print(register T a,register char x=0){
		if(x) *--outs = x, x = 0;
		
		if(!a)*--outs = '0';
		else 
			while(a)
				*--outs = (a % 10) + 48, a /= 10;
		
		if(x)
			*--outs = x;
		
		fwrite(outs, outr - outs , 1, stdout);
		outs = outr;
	}
};

using io :: print;
using io :: inp;
using io :: inpu;
using io :: inp_ll;

using i32 = int;
using i64 = long long;
using u8 = unsigned char;
using u32 = unsigned;
using u64 = unsigned long long;
using f64 = double;
using f80 = long double;

ll power(ll a, ll b, ll p)
{
	if (!b) return 1;
	ll t = power(a, b/2, p);
	t = t*t%p;
	if (b&1) t = t*a%p;
	return t;
}

const int MAXN = 200010;
const u64 MOD = 1000000007;
const f80 MI = f80(1)/MOD;
const int INF = 1000000010;

int n;
ll costX;
ll x[MAXN];
ll s[MAXN];

int main()
{
	freopen("try.in", "r", stdin);
	freopen("try.out", "w", stdout);
	
	n = inp();
	costX = inp();
	for (int i = 1; i <= n; ++ i)
	{
		x[i] = inp();
		s[i] = s[i-1]+x[i];
	}
	ll ans = 1LL<<62;
	for (int k = 1; k <= n; ++ k)
	{
		ll cost = k*costX;
		for (int i = n, c = 1; i >= 1; i -= k, c ++)
		{
			int j = max(i-k, 0);
			cost += (s[i]-s[j])*(c == 1 ? 5 : 2*c+1);
		}
		ans = min(ans, cost);
	}
	ans += n*costX;
	cout << ans << endl;
	
	return 0;
}


Compiler output:
a.cc:67:38: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
   67 |         inline void print(register T a,register char x=0){
      |                                      ^
a.cc:67:56: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
   67 |         inline void print(register T a,register char x=0){
      |                                                        ^
a.cc: In function 'int main()':
a.cc:139:14: error: ambiguous overload for 'operator<<' (operand types are 'std::ostream' {aka 'std::basic_ostream<char>'} and 'll' {aka '__int128'})
  139 |         cout << ans << endl;
      |         ~~~~ ^~ ~~~
      |         |       |
      |         |       ll {aka __int128}
      |         std::ostream {aka std::basic_ostream<char>}
In file included from /usr/include/c++/14/istream:41,
                 from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127,
                 from a.cc:3:
/usr/include/c++/14/ostream:174:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  174 |       operator<<(long __n)
      |       ^~~~~~~~
/usr/include/c++/14/ostream:178:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  178 |       operator<<(unsigned long __n)
      |       ^~~~~~~~
/usr/include/c++/14/ostream:182:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  182 |       operator<<(bool __n)
      |       ^~~~~~~~
In file included from /usr/include/c++/14/ostream:1022:
/usr/include/c++/14/bits/ostream.tcc:96:5: note: candidate: 'std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char; _Traits = std::char_traits<char>]'
   96 |     basic_ostream<_CharT, _Traits>::
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/ostream:189:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  189 |       operator<<(unsigned short __n)
      |       ^~~~~~~~
/usr/include/c++/14/bits/ostream.tcc:110:5: note: candidate: 'std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char; _Traits = std::char_traits<char>]'
  110 |     basic_ostream<_CharT, _Traits>::
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/ostream:200:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  200 |       operator<<(unsigned int __n)
      |       ^~~~~~~~
/usr/include/c++/14/ostream:211:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  211 |       operator<<(long long __n)
      |       ^~~~~~~~
/usr/include/c++/14/ostream:215:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  215 |       operator<<(unsigned long long __n)
      |       ^~~~~~~~
/usr/include/c++/14/ostream:231:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  231 |       operator<<(double __f)
      |       ^~~~~~~~
/usr/include/c++/14/ostream:235:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(float) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  235 |       operator<<(float __f)
      |       ^~~~~~~~
/usr/include/c++/14/ostream:243:7: note: candidate: 'std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long double) [with _CharT = char; _Traits = std::char_traits<char>; __ostream_type = std::basic_ostream<char>]'
  243 |       operator<<(long double __f)
      |       ^~~~~~~~
/usr/include/c++/14/ostream:573:5: note: candidate: 'std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, char) [with _CharT = char; _Traits = char_traits<char>]'
  573 |     operator<<(basic_ostream<_CharT, _Traits>& __out, char __c)
      |     ^~~~~~~~
/usr/include/c++/14/ostream:579:5: note: candidate: 'std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, char) [with _Traits = char_traits<char>]'
  579 |     operator<<(basic_ostream<char, _Traits>& __out, char __c)
      |     ^~~~~~~~
/usr/include/c++/14/ostream:590:5: note: candidate: 'std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, signed char) [with _Traits = char_traits<char>]'
  590 |     operator<<(basic_ostream<char, _Traits>& __out, signed char __c)
      |     ^~~~~~~~
/usr/include/c++/14/ostream:595:5: note: candidate: 'std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, unsigned char) [with _Traits = char_traits<char>]'
  595 |     operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c)
      |     ^~~~~~~~