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

class Graph2 {
	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 Graph2() { 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 ++) {
				adjWeight[i][j] = in.nextInt();
			}
		}
		int u, v;
		for(i = 0; i < totalVertex; i ++) {
			for(j = 0; j < totalVertex; j ++) {
				if( adjWeight[i][j] == -1) {
					adjMatrix[i][j] = 0;
				}
				else {
					adjMatrix[i][j] = 1;
				}
			}	
		}
		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[] MST(int s) {
		int[] dists = new int[totalVertex];
		for(int n = 0; n< dists.length; n++) {
			dists[n] = Integer.MAX_VALUE;
		}
			
		
		//root = s
		int root = s;
		int cur = root;
		dists[cur] = 0;
		for(int i = 0; i < totalVertex; i++) { //change 3 to totalVertex Later
			//find vertex v that is closest to s (with minimum dist) 
			//(implementation detail for this step determines the asymptotic complexity of the algorithm)
			cur = getUnsettledNearest(dists);
        	//update dist[x] for every neighbor x of v: dist[x]=min{dist[v]+weight(v->x),dist[x]}
			LinkedList<Integer> neighbors = getUnsettledNeighbors(cur);
			for(int n:neighbors) {
				dists[n] = Math.min((getWeight(cur,n)), dists[n]);

			}
       		ifSettled[cur] = true;
		}
		
		return dists;
	}
}

public class Main {
	public static void main(String[] argv) {
		Graph2 g = new Graph2();
		g.loadAdjMatrix();
		int[] dist = g.MST(0);
		int sum = 0;
		for(int i = 0; i < g.getTotalVertex(); i ++) {
			sum += dist[i];
		}
		System.out.println(sum);
	}
}


Measured memory_bytes: 40616