#pragma GCC optimize("O3")
#include<bits/stdc++.h>
using namespace std;
#define rc(x) return cout<<x<<endl,0
#define pb push_back
#define dbg(x) cout << #x << '=' << x << '\n';
#define ll long long
#define sz size()
#define x first
#define y second
#define pi pair <int, int>
#define pii pair <pi, pi>
#define vi vector <ll>
#define in insert
#define er erase
#define fd find
int n, dp2, dp1, ans;

int32_t main(){
	ios_base::sync_with_stdio(0);cin.tie(0);cerr.tie(0);cout.tie(0);
	ifstream cin("ssm.in");
	ofstream cout("ssm.out");
	cin>>n;
	for(int i=1; i<=n; i++){
        int x;
        dp2=max(dp1+x, x);
        dp1=dp2;
        ans=max(dp1, ans);
	}
	cout<<ans;
}