def is_valid_expression(s):
    valid_chars = set("0123456789+-*/ ")
    if any(c not in valid_chars for c in s):
        return False
    
    prev_char = ''
    for i, c in enumerate(s.strip()):
        if c in '+-*/':
            if prev_char in '+-*/' or i == 0 or i == len(s.strip()) - 1:
                return False
        prev_char = c
    
    return True

def evaluate_expression(s):
    try:
        result = eval(s)
        if isinstance(result, int):
            return result
        else:
            return -1
    except ZeroDivisionError:
        return -1
    except Exception:
        return -1

def integer_calculator(s):
    s = s.strip()
    
    if not is_valid_expression(s):
        return -1
    
    result = evaluate_expression(s)
    
    return result

#include <bits/stdc++.h>
using namespace std;

struct node {
    int h[26];
    int n;     
}

node null;
vector<node> trie; 
void addContact(string &name) {
    int act = 0; 
    for (char c : name) {
        int p = c - 'a'; 
        if (!trie[act].h[p]) { 
            trie[act].h[p] = trie.size();
            trie.push_back(null);
        }
        act = trie[act].h[p]; 
        trie[act].n++;
    }
}

int findPartial(string &prefix) {
    int act = 0; 
    for (char c : prefix) {
        int p = c - 'a'; 
        if (!trie[act].h[p]) return 0; 
        act = trie[act].h[p]; 
    }
    return trie[act].n; 
}

int main() {
    int n;
    cin >> n; 
    string operation, contact;

    null.n = 0;
    for (int i = 0; i < 26; i++) null.h[i] = 0;
    trie.push_back(null);

    vector<int> results; 

    for (int i = 0; i < n; i++) {
        cin >> operation >> contact;
        if (operation == "add") {
            addContact(contact);
        } else if (operation == "find") {
            results.push_back(findPartial(contact)); 
        }
    }

    for (int res : results) {
        cout << res << "\n";
    }

    return 0;
}

#include <iostream>
#include <vector>
using namespace std;

vector<int> frequencyOfMaxValue(vector<int>& numbers, vector<int>& queries) {
    int n = numbers.size();
    vector<int> answer(n, -1);   
    int maxvalue = -1;           
    int count = 1;              
    for (int i = n - 1; i >= 0; --i) {
        if (numbers[i] == maxvalue) {
            count++;
        } else if (numbers[i] > maxvalue) {
            maxvalue = numbers[i];
            count = 1;
        }
        answer[i] = count;       
    }

    vector<int> result;
    for (int index : queries) {
        result.push_back(answer[index - 1]);  
    }

    return result;
}

#include <bits/stdc++.h>
using namespace std;
vector<int> getPopularityOrder(vector<vector<int>> song_preferences) {
    int n = song_preferences[0].size();
    vector<vector<int>> boxScore(n, vector<int>(n, 0));
    for (const vector<int>& pref : song_preferences) {
        for (int i = 0; i < pref.size() - 1; i++) {
            for (int j = i + 1; j < pref.size(); j++) {
                boxScore[pref[i]][pref[j]] += 1;
            }
        }
    }

    vector<array<int, 2>> wins(n, {0, 0});
    for (int i = 0; i < n; i++) {
        wins[i][0] = i; 
        for (int j = i + 1; j < n; j++) {
            int score = boxScore[i][j] - boxScore[j][i];
            if (score >= 0) {
                wins[i][1]++;
            } else {
                wins[j][1]++;
            }
        }
    }

    sort(wins.begin(), wins.end(), [](const array<int, 2>& a, const array<int, 2>& b) {
        if (a[1] == b[1]) {
            return a[0] < b[0];
        } else {
            return b[1] < a[1];
        }
    });

    vector<int> result;
    for (const auto& win : wins) {
        result.emplace_back(win[0]);
    }

    return result;
}

def find_smallest_k(mat, n):
    for k in range(n):
        row_condition = all(mat[k][j] == 0 for j in range(n) if j != k)
        column_condition = all(mat[i][k] == 1 for i in range(n) if i != k)
        
        if row_condition and column_condition:
            return k
            
    return -1
n = int(input())
mat = []
for _ in range(n):
    mat.append(list(map(int, input().split())))
result = find_smallest_k(mat, n)
print(result)