#include<fstream.h>
ifstream f("graf.in");
ofstream g("graf.out");
int a[21][21],n,viz[21],c[21];
void citire()
{f>>n;
for(int i=1;i<=n;i++)
	for(int j=1;j<=n;j++)f>>a[i][j];f.close();}
int convex()
{int p=1;
int u=1;
c[1]=1;
viz[1]=1;while(p<=u){int x=c[p];
for(int i=1;i<=n;i++)
	if(a[x][i]==1 && viz[i]==0) {c[1+u]=i;
								viz[i]=1;}
		p++;}
for (int i=1;i<=n;i++)
	if(viz[i]==0)return 0;
	return 1;}
int main()
{citire();
if(convex())g<<"graf conex";
else g<<"nu este";
return 0;
g.close();
}