input()
a=[*map(int,input().split())]
print(['chest','biceps','back'][max(0,1,2,key=lambda i: sum(a[i::3]))])#include <iostream>
using namespace std;
int main()
{
int n,a[3]={0,0,0},b;
cin>>n;
for(int i=0;i<n;i++)
{
cin>>b;
a[i%3]+=b;
}
if(a[0]>a[1]&&a[0]>a[2])
cout<<"chest"<<endl;
if(a[1]>a[0]&&a[1]>a[2])
cout<<"biceps"<<endl;
if(a[2]>a[1]&&a[2]>a[0])
cout<<"back"<<endl;
return 0;
}
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