#include<iostream>
#include<math.h>
#include<vector>

using namespace std;

int main(){
  double n;
  double now;
  double a;
  cin >> n;
  cin >> a;
  now = a;
  for(int i=1;i<n;i++){
    cin >> a;
    if(a > 1){
      now *= a;
    }else if(a == 1){
      now++;
    }else{
      now -= a;
    }
  }
  cout << now << endl;
}