#include <iostream>

#include <algorithm>

#include <vector>

using namespace std;

int main(){

    int n;

    cin >> n;

    vector<int> a(n);

    for(int i =  ; i < n; ++ i)

        cin >> a[i];

    int maxlen = ;

    if(n == ) maxlen = ;

    else if(n == ) maxlen = ;

    else{

        maxlen = ;

        int l = , r =;

        for(int i = ; i < n; ++ i){

            if(a[i] == a[i-] + a[i-]){

                r = i;

                if(maxlen < r-l+){

                    maxlen = r-l+;

                }

            }

            else{

                l = i-;

            }

        }

    }

    cout<<maxlen<<endl;

    return ;

}