#include <bits/stdc++.h> 
int f(int ind,vector<int>&nums,vector<int>&dp)
{
    
    if(ind==0)
      return nums[ind];
    if(ind <1)
       return 0;

       if(dp[ind]!=-1)
      return dp[ind];
    int pick=nums[ind]+f(ind-2,nums,dp);
    int notp=0+f(ind-1,nums,dp);
    dp[ind]=max(pick,notp);
    return max(pick,notp);
}
int maximumNonAdjacentSum(vector<int> &nums){
    // Write your code here.
    int n=nums.size();
    vector<int> dp(n,-1);
    return f(n-1,nums,dp);
}