#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

vector<vector<int>> graf;
vector<int> used;
int k = 0;

void dfs(int v) {
    k++;
    used[v] = 1;
    for (auto& el : graf[v]) {
        if (used[el] == 0) {
            dfs(el);
        }
    }
}

int main()
{
    ios::sync_with_stdio(false);
    int n, ans = 0;
    cin >> n;
    graf.resize(n);
    used.resize(n);
    for (auto& el : used) {
        el = 0;
    }
    for (int i = 0; i != n; i++) {
        for (int j = 0; j != n; j++) {
            int x;
            cin >> x;
            if (x == 1) {
                graf[i].push_back(j);
                ans++;
            }
        }
    }
    ans /= 2;
    dfs(0);
    if (k == n && ans==n-1) {
        cout << "YES";
    }
    else {
        cout << "NO";
    }
    return 0;
}