#include<bits/stdc++.h> using namespace std; int max(int x,int y) { if (x>y) return x; if (x<=y) return y; } int main() { int a; cin>>a; int byd[a+1],dp[a+1]; for (int i=1;i<=a;i++) { cin>>byd[i]; dp[i]=0; } dp[0]=0; dp[1]=byd[1]; for (int i=2;i<=a;i++) { dp[i]=max(dp[i-1],(byd[i]+dp[i-2])); } cout<<dp[a]; return 0; }