#include <iostream>
#include<bits/stdc++.h>
#include<utility>
#include <queue>
#define ll long long
#define ull unsigned long long
#define pi  3.14159

#define OO  2000000000
//#define ceil(w, m) (((w) / (m)) + ((w) % (m) ? 1 : 0))
using namespace std;

void yasmeen_fakhri(){
  ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
  #ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
  #endif
}

int main() {
   yasmeen_fakhri();
   int n;   cin>>n;
   int arr[n];
   for(int i =1 ; i<=n ; i++){
       cin>>arr[i];
   }
   int a=0 , b=0 , c=0 ;
   for(int i =1 ; i<=n ; i++){
       if      (i % 3 == 1) a+=arr[i];
       else if (i % 3 == 2) b+=arr[i];
       else if (i % 3 == 0) c+=arr[i];
   }
   int maxx = INT_MIN;
   maxx = max(max(a,b),c);
   if       (maxx == a) cout<<"chest";
   else if  (maxx == b) cout<<"biceps";
   else if  (maxx == c) cout<<"back";
return 0;
}