#include <bits/stdc++.h>
#include <stdio.h>
#include <iostream>
#include <vector>

using namespace std;

int c[110];


vector <int> r[110];

void dfs(int v){

c[v]=1;

for(int i=0;i<r[v].size();i++)if(c[r[v][i]]==0)dfs(r[v][i]);

}

int main()
{
    freopen ("Input.txt", "r", stdin);
    freopen ("Output.txt", "w", stdout);
    int n,s,a,b,ans=0;
    cin>>n;
    for(int i=0;i<n;i++){
        c[i]=0;
    }
    for(int i=0;i<n;i++){
        for(int j=0;j<n;j++){
            cin>>a;
            if(a==1){
                r[i].push_back(j);
                ans++;
            }
        }
    }
    if(ans/2!=n-1){
        cout<<"NO";
        return 0;
    }
    dfs(0);
    for(int i=0;i<n;i++){
        if(c[i]==0){
            cout<<"NO";
            return 0;
        }
    }
    cout<<"YES";
    return 0;
}