import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;

class PGraph {
	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 PGraph() { 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 != -1) {
				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) {
		Set<Integer> settled = new HashSet<Integer>();
		int[] distancesFromSource = new int[this.getTotalVertex()];

		
		 for(int i = 0; i < distancesFromSource.length; i++) {
	            distancesFromSource[i] = Integer.MAX_VALUE;
	            ifSettled[i] = false;
	        }
		 distancesFromSource[s] = 0;
		 
		 LinkedList<Integer> unsettled = getUnsettledNeighbors(s);
		 
		 while(settled.size() != totalVertex) {
			 int next = getUnsettledNearest(distancesFromSource);
			 settled.add(next);
			 ifSettled[next] = true;
			 
			 LinkedList<Integer> neighbors = getUnsettledNeighbors(next);
			 
			 for(int i = 0; i < neighbors.size(); i++) {
				 int nextNeighbor = neighbors.get(i);
				
					 distancesFromSource[nextNeighbor] = Math.min( 
							 getWeight(next, nextNeighbor), distancesFromSource[nextNeighbor]);
			 }
			
			
			 
		 }
		 return distancesFromSource;

	}
}

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



Measured memory_bytes: 40580