#include <bits/stdc++.h> 

int maximumNonAdjacentSum(vector<int> &nums){
    // Write your code here.
    int n=nums.size();

    int prev2=0;
    int pre=nums[0],curri=0;

    for(int i=1;i<n;i++)
    {
        int pick=nums[i];
        if(i>1)
         pick+=prev2;
         
        int notp=0+pre;
        curri=max(pick,notp);
        prev2=pre;
        pre=curri;
    }
    return pre;
}