#include<bits/stdc++.h>
using namespace std;
int N;
constexpr long double hz[]={436.0,490.5,261.6,294.3,327.0,348.8,392.4};
int main(){
  cin>>N;
  vector<long double> v(N);
  for(auto& x:v)cin>>x;
  long double sa[7]={};
  for(int i=0;i<7;++i){
    int j=round(44100/hz[i]);
    for(int k=0;k+j<N;++k){
      sa[i]+=(v[k]-v[k+j])*(v[k]-v[k+j]);
    }
  }
  auto id=min_element(sa,sa+7)-sa;
  putchar('A'+id);
  puts("4");
}