#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>

#include <functional>
#include <cassert>

typedef long long ll;
using namespace std;

#define debug(x) cerr << #x << " = " << (x) << endl;


#define mod 1000000007 //1e9+7(prime number)
#define INF 1000000000 //1e9
#define LLINF 2000000000000000000LL //2e18
#define SIZE 100010

int main(){
  int n,a;
  ll ans1 = 0, ans2 = 0;
  
  scanf("%d",&n);

  for(int i=0;i<n;i++){
    scanf("%d",&a);

    ll n_ans1 = ans1, n_ans2 = ans2;
    
    if(n_ans1 == 0 || n_ans1 == 1 || abs(a) <= 1){
      ans1 = n_ans1 + abs(a);
    }else{
      if(a > 0){
        ans1 = n_ans1 * a;
      }else{
        ans2 = n_ans1 * a;
      }
    }
    
    if(n_ans2 == 0 || n_ans1 == -1 || abs(a) <= 1){
      ans2 = n_ans2 - abs(a);
    }else{
      if(a > 0){
        ans2 = n_ans2 * a;
      }else{
        ans1 = n_ans2 * a;
      }
    }    
  }

  printf("%lld\n",ans1);
  
  return 0;
}