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#include <iostream>
#include <fstream>
#include <vector>
#include <limits>
#include <algorithm>


int n;


struct Cost
{
	int a, b;
	int c;
	bool used;
};


std::vector<Cost> costs;



void read(std::istream & str)
{
Cost c;

	str >> n;
	costs.reserve((n*n)/2 + n);

	for(int i=0 ; i < n ; ++i)
	{
		for(int x=0 ; x < n-i ; ++x)
		{
			c.a = i;
			c.b = i + x;
			c.used = false;
			str >> c.c;

			costs.push_back(c);
		}
	}
}



void calc()
{
long sum = 0;
int size = 0;

	std::sort(costs.begin(), costs.end(), [](const Cost & c1, const Cost & c2)->bool{return c1.c < c2.c;});

	for(int in = 0 ; in < n ; ++in)
	{
		for(size_t i=0 ; i<costs.size() ; ++i)
		{
			Cost & c = costs[i];

			if( c.a <= in && c.b >= in )
			{
				if( !c.used )
				{
					size += 1;
					c.used = true;
					sum += c.c;
				}

				break;
			}
		}
	}

	for(size_t i=0 ; i<costs.size() && size < n ; ++i)
	{
		Cost & c = costs[i];

		if( !c.used )
		{
			size += 1;
			sum += c.c;
			c.used = true;
		}
	}

	std::cout << sum << std::endl;
}




int main()
{
	std::cin.sync_with_stdio(false);

	read(std::cin);
	calc();

return 0;
}