import java.util.*;
 
public class Main{
 
  public static void main(String[] args){
  
    Scanner sc = new Scanner(System.in);
    ArrayList<Double> nums = new ArrayList<>();
    double a = 0;
    int i = 0;
    
    while(sc.hasNext()){
    	nums.add(sc.nextDouble());
    }
    
    for(double num : nums){
      if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      }
    }
    
    System.out.println(1/a);
    
  }
} import java.util.*; util.* java public class Main{
 
  public static void main(String[] args){
  
    Scanner sc = new Scanner(System.in);
    ArrayList<Double> nums = new ArrayList<>();
    double a = 0;
    int i = 0;
    
    while(sc.hasNext()){
    	nums.add(sc.nextDouble());
    }
    
    for(double num : nums){
      if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      }
    }
    
    System.out.println(1/a);
    
  }
} Main public static void main(String[] args){
  
    Scanner sc = new Scanner(System.in);
    ArrayList<Double> nums = new ArrayList<>();
    double a = 0;
    int i = 0;
    
    while(sc.hasNext()){
    	nums.add(sc.nextDouble());
    }
    
    for(double num : nums){
      if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      }
    }
    
    System.out.println(1/a);
    
  } main {
  
    Scanner sc = new Scanner(System.in);
    ArrayList<Double> nums = new ArrayList<>();
    double a = 0;
    int i = 0;
    
    while(sc.hasNext()){
    	nums.add(sc.nextDouble());
    }
    
    for(double num : nums){
      if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      }
    }
    
    System.out.println(1/a);
    
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) ArrayList<Double> nums = new ArrayList<>(); nums new ArrayList<>() double a = 0; a 0 int i = 0; i 0 while(sc.hasNext()){
    	nums.add(sc.nextDouble());
    } sc.hasNext() sc.hasNext sc {
    	nums.add(sc.nextDouble());
    } nums.add(sc.nextDouble()) nums.add nums sc.nextDouble() sc.nextDouble sc for(double num : nums){
      if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      }
    } double num nums {
      if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      }
    } {
      if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      }
    } if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      } i == 0 i 0 {
        i = 1;
      } i = 1 i 1 {
    	a += 1/num;
      } a += 1/num a 1/num 1 num System.out.println(1/a) System.out.println System.out System System.out 1/a 1 a String[] args args public class Main{
 
  public static void main(String[] args){
  
    Scanner sc = new Scanner(System.in);
    ArrayList<Double> nums = new ArrayList<>();
    double a = 0;
    int i = 0;
    
    while(sc.hasNext()){
    	nums.add(sc.nextDouble());
    }
    
    for(double num : nums){
      if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      }
    }
    
    System.out.println(1/a);
    
  }
} public class Main{
 
  public static void main(String[] args){
  
    Scanner sc = new Scanner(System.in);
    ArrayList<Double> nums = new ArrayList<>();
    double a = 0;
    int i = 0;
    
    while(sc.hasNext()){
    	nums.add(sc.nextDouble());
    }
    
    for(double num : nums){
      if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      }
    }
    
    System.out.println(1/a);
    
  }
} Main
import java.util.*;
 
public class Main{
 
  public static void main(String[] args){
  
    Scanner sc = new Scanner(System.in);
    ArrayList<Double> nums = new ArrayList<>();
    double a = 0;
    int i = 0;
    
    while(sc.hasNext()){
    	nums.add(sc.nextDouble());
    }
    
    for(double num : nums){
      if(i == 0){
        i = 1;
      }else{
    	a += 1/num;
      }
    }
    
    System.out.println(1/a);
    
  }
}