if I change s = 0 and l = n-1. then why not work? LEETCODE–374. Guess Number Higher or Lower

public class Solution extends { THIS IS CLASS
public ( n) {TAKING A NO. N
s = 1;S IS START
l = IS LAST m = 0 m = s + (l-s)/2;M IS MIDDLE while(s<=l)WHILE LOOP`
{

        m = s + (l-s)/2;`MIDDLE`
         g = guess(m);`G IS GIVING 0,1,-1 `
        if(g==0)
        break;
        else if(g==-1)
        l = m-1;
        else
         s = m + 1;
        
    }return m;

    
}

}

I assign s=0 and l =n-1, then why not work. I know its very basic but I am some how confused.