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#include <stdio.h>
#include <algorithm>
#include <list>

struct Position
{
	int x;
	int y;
	
	Position()
	{
	}
	
	Position(int _x, int _y) : x(_x), y(_y)
	{
	}
};

struct Cell
{
	int cost;
	bool done;
};

// GLOBALS
int n;
Cell** costs;
Position* positions;
int allCosts;
int markedCups;
long long int total;

std::list<Position> queue;



// FUNCS
bool mySort(const Position& p1, const Position& p2)
{
	if (costs[p1.y][p1.x].cost == costs[p2.y][p2.x].cost)
		return p1.x - p1.y < p2.x - p2.y;
	else
		return costs[p1.y][p1.x].cost < costs[p2.y][p2.x].cost;
}


void markDone(int p1x, int p1y, int p2x, int p2y, int p3x, int p3y)
{
	Cell& c1 = costs[p1y][p1x];
	Cell& c2 = costs[p2y][p2x];
	Cell& c3 = costs[p3y][p3x];
	
	if (c1.done && c2.done && !c3.done)
	{
		c3.done = true;
		//printf("MARK: %d %d\n", p3x, p3y);
		queue.push_back(Position(p3x, p3y));
		if (p3x == p3y)
			markedCups++;
	}
	else if (c1.done && !c2.done && c3.done)
	{
		c2.done = true;
		//printf("MARK: %d %d\n", p2x, p2y);
		queue.push_back(Position(p2x, p2y));
		if (p2x == p2y)
			markedCups++;
	}
	else if (!c1.done && c2.done && c3.done)
	{
		c1.done = true;
		//printf("MARK: %d %d\n", p1x, p1y);
		queue.push_back(Position(p1x, p1y));
		if (p1x == p1y)
			markedCups++;
	}
}

void process(int px, int py)
{
	//printf("PROCESS: %d %d\n", px, py);
	costs[py][px].done = true;
	
	for (int x = py; x < n; ++x)
	{
		if (x < px)
		{
			//int sy = 
			markDone(x, py, px, py, px, py + x - py + 1);
		}
		else if (x > px)
		{
			markDone(px, py, x, py, x, py + px - py + 1);
		}
	}
	
	for (int y = 0; y < px; ++y)
	{
		if (y < py)
		{
			markDone(px, py, px, y, py - 1, y);
		}
	}
	
	
	
	/*for (int i = 0; i < n; ++i)
	{
		for (int j = 0; j < n; j++)
			printf("[%d-%d] ", costs[i][j].cost, costs[i][j].done);
		printf("\n");
	}*/
}

int main()
{
	scanf("%d", &n);
	
	allCosts = (n + 1) * n / 2;
	costs = new Cell*[n];
	positions = new Position[allCosts];

	int positionIndex = 0;
	for (int i = 0; i < n; ++i)
	{
		costs[i] = new Cell[n];
		for (int j = 0; j < n; j++)
		{
			if (j < i)
				costs[i][j].cost = 0;
			else
			{
				scanf("%d", &(costs[i][j].cost));
				positions[positionIndex].x = j;
				positions[positionIndex].y = i;
				positionIndex++;
			}
			
			costs[i][j].done = false;
		}
	}
	
	std::sort(positions, positions + allCosts, mySort);
	
	markedCups = 0;
	total = 0;
	for (int i = 0 ; i < allCosts; i++)
	{
		int px = positions[i].x;
		int py = positions[i].y;
		
		if (costs[py][px].done)
			continue;
		
		//printf("-----------------------------------------------------------\n");
		
		total += (long long int)costs[py][px].cost;
		process(px, py);
		
		while (!queue.empty())
		{
			Position& cell = queue.front();
			process(cell.x, cell.y);
			queue.pop_front();
		}
		
		if (markedCups == n)
			break;
	}
	
	printf("%lld", total);
	
	delete[] positions;
	for (int i = 0; i < n; ++i)
		delete[] costs[i];
	delete[] costs;
	return 0;
}