#include <bits/stdc++.h>
using namespace std;
#define fast ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define ll long long
#define mp make_pair
#define se second
#define fi first
int main()
{
int m;
cin>>m;
int n = 2*m;
int a[n], b[n];
pair <int, int> mxaa[n], mxab[n], mxbb[n], mxba[n];
for(int i = 0; i<n; i++)
{
cin>>a[i];
}
for(int i = 0; i<n; i++)
{
cin>>b[i];
}
for(int i = 0; i<n; i++)
{
mxaa[i] = mp(-1,-1);
mxab[i] = mp(-1,-1);
mxba[i] = mp(-1,-1);
mxbb[i] = mp(-1,-1);
}
mxaa[0].fi = 1;
mxbb[0].fi = 1;
mxab[0].fi = 0;
mxba[0].fi = 0;
for(int i = 1; i<n; i++)
{
if(a[i] >= a[i-1])
{
mxaa[i] = max(mxaa[i], mp(mxaa[i-1].fi+1, 0));
mxab[i] = max(mxab[i], mp(mxab[i-1].fi, 0));
}
if(a[i] >= b[i-1])
{
mxaa[i] = max(mxaa[i], mp(mxba[i-1].fi+1, 1));
mxab[i] = max(mxab[i], mp(mxbb[i-1].fi, 1));
}
if(b[i] >= a[i-1])
{
mxba[i] = max(mxba[i], mp(mxaa[i-1].fi, 0));
mxbb[i] = max(mxbb[i], mp(mxab[i-1].fi+1, 0));
}
if(b[i] >= b[i-1])
{
mxba[i] = max(mxba[i], mp(mxba[i-1].fi, 1));
mxbb[i] = max(mxbb[i], mp(mxbb[i-1].fi+1, 1));
}
}
int ans = -1;
if(mxaa[n-1].fi >= m && mxab[n-1].fi >= m)
{
ans = 0;
}
if(mxba[n-1].fi >= m && mxbb[n-1].fi >= m)
{
ans = 1;
}
if(ans == -1)
{
cout<<ans;
return 0;
}
int plana[n], planb[n];
plana[n-1] = ans;
planb[n-1] = ans;
for(int i = n-1; i>0; i--)
{
if(plana[i] == 0)
{
plana[i-1] = mxaa[i].se;
}
if(plana[i] == 1)
{
plana[i-1] = mxba[i].se;
}
if(planb[i] == 0)
{
planb[i-1] = mxab[i].se;
}
if(planb[i] == 1)
{
planb[i-1] = mxbb[i].se;
}
}
int alead = m, blead = m;
if(ans == 0)
{
alead = mxaa[n-1].fi;
blead = mxab[n-1].fi;
}
if(ans == 1)
{
alead = mxba[n-1].fi;
blead = mxbb[n-1].fi;
}
/*
for(int i = 0; i<n; i++)
{
cout<<plana[i]<<" "<<planb[i]<<endl;
}
cout<<alead<<blead<<endl;
*/
assert(alead >= m && blead >= m);
int loc = n;
while(alead != m && blead != m)
{
assert(loc >= 0);
loc--;
if(plana[loc] == planb[loc])
{
continue;
}
if(plana[loc] == 0 && a[loc] >= b[loc])
{
blead--;
planb[loc] = 0;
}
else if(plana[loc] == 0 && b[loc] >= a[loc])
{
alead--;
plana[loc] = 1;
}
else if(plana[loc] == 1 && a[loc] >= b[loc])
{
alead++;
plana[loc] = 0;
}
else if(plana[loc] == 1 && b[loc] >= a[loc])
{
blead++;
planb[loc] = 1;
}
}
string S = "";
if(alead == m && ans != -1)
{
for(int i = 0; i<n; i++)
{
if(plana[i] == 0)
S+="A";
else
S+="B";
}
}
else if(blead == m && ans != -1)
{
for(int i = 0; i<n; i++)
{
if(planb[i] == 0)
S+="A";
else
S+="B";
}
}
cout<<S;
cout<<endl;
}
