/*
[ SAMPLE SOURCE CODE FOR "TEAM CONTEST" SUBTASK 5 ]
Algorithm: Please refer to the editorial.
Time Complexity: O(MAX^3)
*/
#include <vector>
#include <cassert>
#include <iostream>
#include <algorithm>
using namespace std;
int main() {
// step #1. read input
cin.tie(0);
ios_base::sync_with_stdio(false);
int N;
cin >> N;
vector<int> X(N), Y(N), Z(N);
for (int i = 0; i < N; i++) {
cin >> X[i] >> Y[i] >> Z[i];
}
// step #2. record in 3D array
int SX = *max_element(X.begin(), X.end()) + 1;
int SY = *max_element(Y.begin(), Y.end()) + 1;
int SZ = *max_element(Z.begin(), Z.end()) + 1;
assert(SX <= 301 && SY <= 301 && SZ <= 301);
vector<vector<vector<bool> > > exists(SX, vector<vector<bool> >(SY, vector<bool>(SZ, false)));
for (int i = 0; i < N; i++) {
exists[X[i]][Y[i]][Z[i]] = true;
}
// step #3. calculate 3D cumulative sum
vector<vector<vector<int> > > sum(SX + 1, vector<vector<int> >(SY + 1, vector<int>(SZ + 1)));
for (int i = 0; i < SX; i++) {
for (int j = 0; j < SY; j++) {
for (int k = 0; k < SZ; k++) {
sum[i + 1][j + 1][k + 1] = (exists[i][j][k] ? 1 : 0);
}
}
}
for (int i = 0; i < SX; i++) {
for (int j = 0; j < SY; j++) {
for (int k = 0; k < SZ; k++) {
sum[i + 1][j + 1][k + 1] += sum[i][j + 1][k + 1];
}
}
}
for (int i = 0; i < SX; i++) {
for (int j = 0; j < SY; j++) {
for (int k = 0; k < SZ; k++) {
sum[i + 1][j + 1][k + 1] += sum[i + 1][j][k + 1];
}
}
}
for (int i = 0; i < SX; i++) {
for (int j = 0; j < SY; j++) {
for (int k = 0; k < SZ; k++) {
sum[i + 1][j + 1][k + 1] += sum[i + 1][j + 1][k];
}
}
}
// step #4. brute force
int answer = -1;
for (int x = 1; x < SX; x++) {
for (int y = 1; y < SY; y++) {
for (int z = 1; z < SZ; z++) {
int sumx = sum[x + 1][y][z] - sum[x][y][z];
int sumy = sum[x][y + 1][z] - sum[x][y][z];
int sumz = sum[x][y][z + 1] - sum[x][y][z];
if (sumx >= 1 && sumy >= 1 && sumz >= 1) {
answer = x + y + z;
}
}
}
}
// step #5. output the answer
cout << answer << endl;
return 0;
}
