//#pragma comment(linker, "/STACK:16777216")
#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<vector>
#include<cstring>
#include<string>
#define mp make_pair
#define scn second
#define frs first
#define pb push_back
#define NAME "INPUT"
using namespace std;
const unsigned long long P=239017, MaxN=2100000, INF=100000000;
typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pi;

int F(int a) {
    if (a == 1)
        return 2;
    return 1;

}

vector<int> q;
int d[101], mtr[101][101], n, used[101];

int get_answer(int s) {
    q.clear();
    q.pb(s);
    for (int i = 1; i <= n; ++i)
        d[i] = 0;
    int p = 0, ans = 0;
    d[s] = 1;

    while(p < q.size()) {
        int v = q[p++];
        for (int i = 1; i <= n; ++i) {
            if (mtr[v][i] && !used[i]) {
                if (d[v] == d[i]) {
                    d[i] = 2;
                    continue;
                }
                if (d[i] == 0) {
                    d[i] = F(d[v]);
                    q.pb(i);
                }
            }
        }
    }
    for (int i = 1; i <= n; ++i) {
        if (d[i] == 1)
            used[i] = 1;
    }
    for (int i = 1; i <= n; ++i) {
        if (d[i] == 2) {
            ans = max(ans, get_answer(i));
        }
    }
    return ans + 1;
}


int main(){

    freopen("INPUT.txt", "r", stdin);
    freopen("OUTPUT.txt", "w", stdout);
    scanf("%d", &n);
    for (int i = 1; i <= n; ++i) {
        for (int j = 1; j <= n; ++j)
            scanf("%d", &mtr[i][j]);
    }
    int ans = 0;
    for (int i = 1; i <= n; ++i) {
        if (!used[i]) {
            ans = max(get_answer(i), ans);
        }

    }
    printf("%d", ans);

    return 0;
}