# include <stdio.h>
int s[10000],n,a[10000][10000];

void citire(){
	int i,j;
	scanf("%d",&n);
	for(i=1;i<n;i++)
		for(j=1;j<n;j++)
			scanf("%d",&a[i][j]);
}

void dfs(int x){
	s[x]=1;
	for(int i=1;i<=n;i++)
		if(a[x][i] && s[i]==0)
			dfs(i);
}

int nr_c(){
	int k=0;	
	for(int i=1;i<=n;i++)
		if(!s[i]){
			dfs(i);
			k++;
		}
	return k;
}

int main(){
	freopen("grafconex.in","r",stdin);
	freopen("grafconex.out","w",stdout);
	citire();
	printf("%d",nr_c());
	return 0;
}