import java.util.LinkedList;
import java.util.Scanner;
import java.util.Iterator;

class Graph_Prim {
	private int totalVertex;
	// adjMatrix[u][v] = 1 if there is an edge from u to v, otherwise 0
	private int[][] adjMatrix;
	// adjWeight[u][v] -- the weight of the edge from u to v if there is one
	private int[][] adjWeight;
	// if a node is settled (e.g., processed in the Dijkstra's algorithm)
	private Boolean[] ifSettled;

	public Graph_Prim() {
		totalVertex = 0;
	}

	public int getTotalVertex() {
		return totalVertex;
	}

	// load graph from standard input
	public void loadAdjMatrix() {
		Scanner in = new Scanner(System.in);
		totalVertex = in.nextInt();
		adjMatrix = new int[totalVertex][totalVertex];
		adjWeight = new int[totalVertex][totalVertex];
		ifSettled = new Boolean[totalVertex];
		int i, j;
		for (i = 0; i < totalVertex; i++) {
			ifSettled[i] = false;
			for (j = 0; j < totalVertex; j++) {
				adjMatrix[i][j] = adjWeight[i][j] = 0;
			}
		}
		int u, v;
		for (i = 0; i < totalVertex; i++) {
			//u = in.nextInt();
			//int degree = in.nextInt();
			for (j = 0; j < totalVertex; j++) {
				v = in.nextInt();
				if (v >= 0)
				{
					adjMatrix[i][j] = 1;
					adjWeight[i][j] = v;
					
				}
			}
		}
		in.close();
	}

	// return weight of the edge from u to v if there is one
	public int getWeight(int u, int v) {
		return adjWeight[u][v];
	}

	// return neighbors of u as a LinkedList
	public LinkedList<Integer> getNeighbors(int u) {
		LinkedList<Integer> tmp = new LinkedList<Integer>();
		for (int v = 0; v < totalVertex; v++) {
			if (adjMatrix[u][v] == 1)
				tmp.add(v);
		}
		return tmp;
	}

	// return unsettled neighbors of u as a LinkedList
	public LinkedList<Integer> getUnsettledNeighbors(int u) {
		LinkedList<Integer> tmp = new LinkedList<Integer>();
		for (int v = 0; v < totalVertex; v++) {
			if ((adjMatrix[u][v] == 1) && (ifSettled[v] == false))
				tmp.add(v);
		}
		return tmp;
	}

	// return the unsettled node that has the smallest dist
	public int getUnsettledNearest(int[] dist) {
		int md = Integer.MAX_VALUE;
		int mv = -1;
		int v;
		for (v = 0; v < totalVertex; v++) {
			if ((ifSettled[v] == false) && (dist[v] < md)) {
				md = dist[v];
				mv = v;
			}
		}
		return mv;
	}

	// implement the following
	public int[] Prim(int s) {
		int distances[] = new int[totalVertex];
		for (int i = 0; i < distances.length; i++) {
			distances[i]= Integer.MAX_VALUE;
		}
		distances[s] = 0;
		int i = 0;
		LinkedList<Integer> explored = new LinkedList<Integer>();
		//int curr = getUnsettledNearest(distances);
		while (explored.size() < totalVertex) {
			int curr = getUnsettledNearest(distances);
			ifSettled[curr] = true;
			explored.add(curr);
			LinkedList<Integer> neighbours = getUnsettledNeighbors(curr);//distances[i]);
			
			for (Integer n : neighbours) {
				distances[n] = Math.min(distances[n], getWeight(curr, n));
			}
			//curr = getUnsettledNearest(distances);
		}
		
		return distances;
	}
}

class Main{
	public static void main(String[] argv) {
		Graph_Prim g = new Graph_Prim();
		g.loadAdjMatrix();
		int[] dist = g.Prim(0);
		int sum = 0;
		for (int i = 0; i < g.getTotalVertex(); i++) {
			//System.out.println(i + " " + dist[i]);
			sum = sum + dist[i];
		}
		System.out.println(sum);
	}
}


Measured memory_bytes: 40872