#include<bits/stdc++.h> #define int long long using namespace std; namespace Fast{ inline long long fr(){ register long long x = 0,f = 1; static char c = getchar(); while (c < '0' || c > '9'){ if (c == '-'){ f = -1; } c = getchar(); } while (c >= '0' && c <= '9'){ x = (x << 1) + (x << 3) + (c ^ 48); c = getchar(); } return x * f; } inline void fw(long long x){ if (x == 0){ putchar('0'); return ; } if (x < 0){ x = -x; putchar('-'); } stack <char> s; while (x){ s.push((x % 10) + 48); x /= 10; } while (!s.empty()){ putchar(s.top()); s.pop(); } } inline void CCF(){ ios::sync_with_stdio(false); cin.tie(0),cout.tie(0); } inline void DEBUG(){ puts("DEBUG"); } } using namespace Fast; int a[114514],dp[114514][2]; signed main(){ int n = fr(); for (int i = 1;i <= n;i++){ a[i] = fr(); } dp[1][1] = a[1]; dp[2][1] = a[2]; dp[2][0] = a[1]; for (int i = 3;i <= n;i++){ dp[i][0] = dp[i - 1][1]; dp[i][1] = max(dp[i - 1][0],dp[i - 2][1]) + a[i]; } cout<<max(dp[n][1],dp[n][0]); return 0; }