问Pangram检测器无法识别每一个pangram

EN

public class Solution {

    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner scan=new Scanner(System.in);
        String s=scan.nextLine();
        s.toLowerCase();
       if(s.length()<26){
           System.out.println("not pangram");
           System.exit(1);
       }
        char arr[]=s.toCharArray();
        int counter=0;
        char c='a';
        for(c='a';c<='z';c++){
            for(int i=0;i<arr.length;i++){
                if(arr[i]==c){
                    counter++;
                    break;
                }
            }
        }
        if(counter==26){
            System.out.println("pangram");
        }
        else{
            System.out.println("not pangram");
        }

    }
}