#include<bits/stdc++.h> using namespace std; const int N = 1000005, inf = 2e9; int n, a[N][2], s[N][2], e[N][2]; int main() { scanf("%d",&n); n *= 2; for(int j=0;j<2;j++) { for(int i=1;i<=n;i++) { scanf("%d",&a[i][j]); } } for(int i=1;i<=n;i++) { for(int j=0;j<2;j++) { s[i][j] = inf, e[i][j] = -inf; for(int k=0;k<2;k++) { if(e[i-1][k] < 0 || a[i-1][k] > a[i][j]) continue; s[i][j] = min(s[i][j], s[i-1][k] + (j==0)); e[i][j] = max(e[i][j], e[i-1][k] + (j==0)); } } } vector<int> ans; if(s[n][0] <= n/2 && n/2 <= e[n][0]) ans.push_back(0); else if(s[n][1] <= n/2 && n/2 <= e[n][1]) ans.push_back(1); else {puts("-1"); return 0;} int L = n/2; for(int i=n;i>1;i--) { int j = ans.back(); if(j == 0) L--; for(int k=0;k<2;k++) { if(e[i-1][k] < 0 || a[i-1][k] > a[i][j]) continue; if(s[i-1][k] <= L && L <= e[i-1][k]) { ans.push_back(k); break; } } } for(int i=n;i--;) { putchar('A' + ans[i]); } puts(""); }

building4.cpp: In function 'int main()':
building4.cpp:9:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
building4.cpp:13:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&a[i][j]);
    ~~~~~^~~~~~~~~~~~~~~