#include #include using namespace std; using LL = long long; using P = pair; using Graph = vector>; const long long LINF = 1LL << 60; #define all(x) (x).begin(), (x).end() #define rep(i,n) for(int i = 0; i < (n); ++i) templatevoid chmin(T&a, T b){if(a > b) a = b;} templatevoid chmax(T&a, T b){if(a < b) a = b;} int main(){ int N; cin >> N; vector V(N); for(int i = 0; i < N; ++i) cin >> V[i]; vector dp(N, 0); dp[0] = V[0]; dp[1] = V[1]; for(int i = 2; i < N; ++i){ chmax(dp[i], dp[i-2]+V[i]); if(i>2)chmax(dp[i], dp[i-3]+V[i]); } cout << dp[N-1] << endl; }