#include<stdio.h>
#include<stdlib.h>
#include<limits.h>
struct node
{
  int node;
  struct node *link;
};

struct node **list;
struct node ** Adjancencylist(int **,int );
void displaylist(struct node **,int );
int bridgeUtil(int,int*,int*,int*,int*);
void bridge(int);
int main()
{
        int **a,n,i,j;
        list=NULL;
	    scanf("%d",&n);
	    a = (int **)malloc(n*sizeof(int *));
	    for(**0;i<n;i++)
        {
        a[i] = (int *)malloc(n*sizeof(int));   
        }
        for(i = 0;i<n;i++)
	    {
           for(j=0;j<n;j++)
           {
            scanf("%d",&a[i][j]);
           }
	    }
       list=Adjancencylist(a,n);
       displaylist(list,n);
       printf("\nBridges in graph\n");
       bridge(n);
       return 0;
}
int bridgeUtil(int u, int visited[], int d[],int l[], int p[])
{
    struct node *temp;
    int i;
    static int t= 0,c=0;
    visited[u] = 1;
    d[u]=l[u] =++t;
    temp=list[u];
   
    while(temp!=NULL)
    {   
        **temp->node;
        int v = i;  
        if (!visited[v])
        {
            p[v] = u;
            bridgeUtil(v,visited,d,l,p);
            if(l[u]<l[v])
            {
            l[u]=l[u];
            }
            else
            {
            l[u]=l[v];
            }
            if (l[v]>d[u])
            {
             printf("%d %d\n",u,v);
             c=c+1;
            }
        }
        else if(v!=p[u])
        {
          if(l[u]<l[v])
          {
          l[u]=l[u];
          }
          else
          {
          l[u]=l[v];}
          }
    temp=temp->link;
    }
    //printf("%d\n",c);

return c;
}
void bridge(int n)
{

    int visited[n];
    int d[n];
    int l[n];
    int p[n];
    int i,c;
    for(**0;i<n;i++)
    {
        p[i] = 0;
        visited[i] = 0;
    }
    for(**0;i<n;i++)
    {
      if(visited[i]==0)
      { 
      c=bridgeUtil(i, visited,d,l,p);
      }
    }
    if(c==0){printf("0\n");}
}

struct node ** Adjancencylist(int **a,int n)
{
	int i,j;
	struct node **list;
	struct node *temp;
	list=(struct node **)malloc(n * sizeof(struct node *));
	for(**0;i<n;i++)
	{
		list[i]=NULL;

		for(j=0;j<n;j++)
		{
		if(a[i][j] != 0)
		{
			if(list[i]==NULL)
			{
				list[i] = (struct node *) malloc(sizeof(struct node));
				temp = list[i];
				temp->node = j;
				temp->link = NULL;
			}
			else
			{
				temp = list[i];
				while(temp->link != NULL)
				temp = temp->link;

				temp->link = (struct node *) malloc(sizeof(struct node));
				temp = temp->link;                                                                 
				temp->node = j;
				temp->link = NULL;
			}
		}
	}
}

return list;
}


void displaylist(struct node **list,int n)
{
	int i;
	struct node * temp;

	printf("Adjacency List Representation:");

	for(**0;i<n;i++)
	{
		temp = list[i];

		if(temp !=NULL)
		printf("\nNode %d is connected to the following nodes ",i);
		while(temp!=NULL)
		{
			printf("%d,",temp->node);
			temp = temp->link;
		}

	}
}