#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
#define ll long long
ll mod = 998244353;
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ll binpow(ll a, ll b)
{
ll res = 1;
while (b>0)
{
if (b&1)
res = (res*a)%mod;
a = (a*a)%mod;
b>>=1;
}
return res;
}
ll gcd(ll x, ll y)
{
if (y==0)
return x;
return gcd(y, x%y);
}
void solve()
{
ll n;
cin>>n;
vector<vector<ll>>v(n+1, vector<ll>(n+1));
for (int i=1 ; i<=n ;i++)
{
for (int j=i ; j<=n ; j++)
cin>>v[i][j];
}
string s1, s2;
ll mx = 0;
for (int i=1 ; i<=n ;i++)
{
if (v[1][i]>mx)
{
mx++;
s1 += 'B';
s2 += 'O';
}
else
{
s2 += 'B';
s1 += 'O';
}
}
ll f = 0;
for (int i=2 ; i<=n ; i++)
{
ll mx = 0;
for (int j=i+1 ; j<=n ;j++)
{
if ((v[i][j]==v[i][j-1] and s1[j]==s1[j-1]) or (v[i][j]!=v[i][j-1] and s1[j]!=s1[j-1]))
{
f = 1;
break;
}
}
}
if (f)
cout<<s2<<endl;
else
cout<<s1<<endl;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
ll tt = 1;
// cin>>tt;
while (tt--)
{
solve();
}
return 0;
}
