import java.util.*;
public class main{
    static int fmax(int[]arr,int i){
        if(i==1) return arr[0];
        return Math.max(arr[i-1],max(arr,i-1));
    }
    public static void main(String[]args){
        Scanner sc = new Scanner(System.in);
       // if(!sc.hasNextInt()){System.out.println("Invalid input");return;}
       try{ 
           int n = sc.nextInt();
        if(n<=0){System.out.println("Invalid input"); return;}
        int [] sales = new int[n];
        for(int i =0;i<n;i++){
            //if(!sc.hasNextInt()){System.out.println("Invalid input");return;}
            sales[i] = sc.nextInt();
            if(sales[i]<0){System.out.println("Invalid input");return;
                
            }
        }
        int max = fmax(sales, n);
        System.out.println(max);
    } catch(Exception e){
        System.out.println("Invalid input");
    }
    }
}