#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef pair<ll,ll> P;
 
long long int INF = 3e18;
double Pi = 3.1415926535897932384626;
 
//vector<ll> G[550010];
//vector<P> tree[500010];
priority_queue <ll> pql;
priority_queue <P> pqp;
//big priority queue
priority_queue <ll,vector<ll>,greater<ll> > pqls;
priority_queue <P,vector<P>,greater<P> > pqps;
//small priority queue
//top pop
 
int dx[8]={1,0,-1,0,1,1,-1,-1};
int dy[8]={0,1,0,-1,1,-1,-1,1};
char dir[] = "DRUL";
//ll bit[500005];
//↓,→,↑,←
 
 
#define p(x) cout<<x<<"\n";
#define el cout<<endl;
#define pe(x) cout<<(x)<<" ";
#define ps(x) cout<<fixed<<setprecision(25)<<x<<endl;
#define pu(x) cout<<(x);
#define pb push_back
#define lb lower_bound
#define ub upper_bound
#define CLEAR(a) a = decltype(a)(); 
 
 
ll mod = 1000000007;
/*
2000000011 is prime
2000000033 is prime
*/

ll rui(ll number1,ll number2){
 
    if(number2 == 0){
        return 1;
    }else{
        ll number3 = rui(number1,number2 / 2);
        number3 *= number3;
        number3 %= mod;
        if(number2%2==1){
            number3 *= number1;
            number3 %= mod;
        }
        return number3;
    }
}
ll gcd(ll number1,ll number2){
 
    if(number1 > number2){
        swap(number1,number2);
    }
    if(number1 == 0 || number1 == number2){
        return number2;
    }else{
        return gcd(number2 % number1,number1);
    }
}
void YES(bool condition){
 
    if(condition){
        p("YES");
    }else{
        p("NO");
    }
    return;
}
void Yes(bool condition){
 
    if(condition){
        p("Yes");
    }else{
        p("No");
    }
    return;
}

/*
ll fact[800005],rfact[800005];

void c3_init(){
    fact[0] = rfact[0] = 1;
    for(ll i=1; i<=800000; i++){
        fact[i] = (fact[i-1]*i) % mod;
    }
    rfact[800000] = rui(fact[800000],mod - 2);
    for(ll i=800000; i>=1; i--){
       rfact[i-1] = rfact[i] * i;
       rfact[i-1] %= mod;
    }
    return;}
ll c3(ll n,ll r){
    return (((fact[n] * rfact[r]) % mod) * rfact[n-r]) % mod;}
*/
 
ll n,m,num,sum,a,b,c,d,e,g,h,w,i,j,q,r,l;
ll k,ans;
ll x[500005],y[500005],z[500005];
char s[50],t[50];
ll table[5000][5000];
ll played[1005];
bool today[1005];

int main(){
    cin >> n;
    for(i=0;i<n;i++){
        for(j=0;j<n-1;j++){
            cin >> table[i][j];
        }
    }
    for(int day=0;day<=n*n;day++){
        for(i=0;i<n;i++){
            today[i] = false;
        }
        int endcount = 0;
        bool update = false;
        for(i=0;i<n;i++){
            if(today[i])continue;
            if(played[i] == n - 1)continue;
            ll op = table[i][played[i]] - 1;
            if(table[op][played[op]] == i+1 && !today[op]){
                //pe(i);p(op);
                played[i]++;
                played[op]++;
                update = true;
                today[i] = true;
                today[op] = true;
            }
        }
        for(i=0;i<n;i++){
            if(played[i] == n - 1){
                endcount++;
            }
        }
        if(endcount == n){
            p(day + 1);
            return 0;
        }
        if(!update){
            p(-1);
            return 0;
        }

    }
    return 0;
}






Measured memory_bytes: 39808