#include <cstdio>#include <cstring>#include <iostream>#include <vector>#include <set>#include <algorithm>using namespace std;const int N = 1000000 ;int n ;int v[N] ;int g[N] ;int main(){ while (~scanf("%d",&n)){ for (int i = 0 ; i < n ; i++) scanf("%d",&v[i]); if (n == 1){ printf("%dn",v[0]) ; continue ; } if (n == 2){ printf("%dn",0); continue ; } memset(g,0,sizeof(g)) ; int ret = 0 ; for (int i = 1 ; i < n ; i++){ int pre = (i>2)?g[i-2]:0 ; int cur = pre + v[i] ; ret = max(ret,cur) ; g[i] = max(g[i-1],cur) ; } memset(g,0,sizeof(g)) ; for (int i = 0 ; i <n-1 ; i++) { int pre = (i>1)?g[i-2]:0 ; int cur = pre + v[i] ; ret = max(ret , cur) ; g[i] = max(g[i-1] , cur) ; } printf("%dn",ret); } return 0 ;}
