Language: Java

import javafx.util.Pair;

import java.util.*;
/*
NOTES:
-more than 10 digits (10^10), use long
-prefix sum of 1's and -1's to control flow of highlighting a region
-log(a)/log(b) = log base b of a
-create a position array if trying to see if elements show up next to each other sequentially
 i.e. elements 1,2,3 are within 3 spots of each other in an array
      arr[scannedInt - 1] = i; (position of i at p[i] in original)
- use a freq array when counting instances of an element occurring
- increment the counter first before simulating anything turn-based (two player game)

 */

public class cf {
    static long mod = (long)(Math.pow(10, 9) + 7);
    public static String alpha = "zabcdefghijklmnopqrstuvwxy";
    public static void main(String[] args) {
        Scanner scan =new Scanner(System.in);
        long n = scan.nextLong();
        long sum = 0;
        int t = 0;
        long tempSum = 0;
        for(; t<10; t++){
            tempSum = sum + (long) Math.pow(26,t+1);
            if(n>=sum && n<=tempSum){
                break;
            }
            sum = tempSum;
        }
        //System.out.println("t "+t);
        Stack<Character> stack = new Stack<>();
        n -= sum;
        //System.out.println(n);
        if(n == Math.pow(26,t+1)){
            for(int i = 0; i<=t; i++)
                stack.push('z');
        }
        else {
            for (int i = 0; i <= t; i++) {
                stack.push(alpha.charAt((int) n % 26));
                n /= 26;
                if(n%26 != 0)
                n += 1;
                //System.out.println("n "+n);
            }
        }
        while(!stack.empty()){
            System.out.print(stack.pop());
        }


        scan.close();
    }





    static int GCD(int a, int b) {
        // Everything divides 0
        if (a == 0) return b;
        if (b == 0) return a;

        // base case
        if (a == b) return a;

        // a is greater
        if (a > b) return GCD(a-b, b);
        return GCD(a, b-a);
    }
    static int LCM(int a, int b){
        return (a*b)/(GCD(a,b));
    }
    static String rev(String s){
        char[] arr = s.toCharArray();
        for(int i = 0; i<(s.length()+1)/2; i++){
            char temp = arr[i];
            arr[i] = arr[s.length()-i-1];
            arr[s.length()-i-1] = temp;
        }
        String fin = new String(arr);
        return fin;
    }
    static long pow(long a, long N) {
        if (N == 0) return 1;
        else if (N == 1) return a;
        else {
            long R = pow(a,N/2);
            if (N % 2 == 0) {
                return R*R;
            }
            else {
                return R*R*a;
            }
        }
    }

    static long powMod(long a, long N) {
        if (N == 0) return 1;
        else if (N == 1) return a % mod;
        else {
            long R = powMod(a,N/2) % mod;
            R *= R;
            R %= mod;
            if (N % 2 == 1) {
                R *= a;
                R %= mod;
            }
            return R % mod;
        }
    }

}

Compiler output:
Main.java:17: error: class cf is public, should be declared in a file named cf.java
public class cf {
       ^
Main.java:1: error: package javafx.util does not exist
import javafx.util.Pair;
                  ^
2 errors