Greg's Workout

#include<stdio.h>
int main()
{
    int a[4]={0},n,m,i;
    scanf("%d",&n);
    for(i=0;i<=n-1;i++)
    {
        scanf("%d",&m);
        a[i%3]+=m;    
    }
    if(a[0]>a[1]&&a[0]>a[2])printf("chest");
    else if(a[1]>a[0]&&a[1]>a[2])printf("biceps");
    else printf("back");
    return 0;
}

http://codeforces.com/contest/255/problem/A