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

void quit(int i) {
    cout << "error " << (i + 1) << '\n';
    exit(0);
}

int main() {
    ios_base::sync_with_stdio(false);
    char c; int n, x, y, a = 0, b = 0; cin >> n;
    for(int i = 0; i < n; ++i) {
        cin >> x >> c >> y;
        if((x + y) % 4 == 1 || (x + y) % 4 == 2) swap(x, y);
        if(x < a || y < b) quit(i);
        if(x > 11 || y > 11) quit(i);
        a = x; b = y;
    }
    cout << "ok\n";
}