codeforce 604B More Cowbell

 1 #include <bits/stdc++.h>
 2 typedef long long ll;
 3 using namespace std;
 4 int main(){
 5         ll n, m, aa[111111];
 6         scanf("%I64d %I64d", &n, &m);
 7         for(ll i = 1 ; i <= n ; i ++)
 8                 scanf("%I64d", &aa[i]);
 9         ll a = m * 2 - n, mx = aa[n];
10         for(int i = 1 ; i <= n - a ; i ++){
11                 mx = max(mx, aa[i] + aa[n - a - i + 1]);
12         }
13         printf("%I64d", mx);
14         return 0;
15 }