import java.util.Scanner;

public class Main {
    private static final int MOD = 1_000_000_007;
    private static final String YES = "Yes";
    private static final String NO = "No";

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        long N = sc.nextLong();

        System.out.println(solve(N));
    }

    private static String solve(long N) {
        long[] num = new long[12+1];
        num[0] = 0;
        for (int i=1; i<12; i++) {
            num[i] = (long)Math.pow(26, i) + num[i-1];
            // System.err.println("i=" + i + " : " + num[i]);
        }



        StringBuilder ans = new StringBuilder();
        for (int i=1; i<=12; i++) {
            if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            }
        }

        return ans.reverse().toString();
    }
} import java.util.Scanner; Scanner java.util public class Main {
    private static final int MOD = 1_000_000_007;
    private static final String YES = "Yes";
    private static final String NO = "No";

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        long N = sc.nextLong();

        System.out.println(solve(N));
    }

    private static String solve(long N) {
        long[] num = new long[12+1];
        num[0] = 0;
        for (int i=1; i<12; i++) {
            num[i] = (long)Math.pow(26, i) + num[i-1];
            // System.err.println("i=" + i + " : " + num[i]);
        }



        StringBuilder ans = new StringBuilder();
        for (int i=1; i<=12; i++) {
            if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            }
        }

        return ans.reverse().toString();
    }
} Main private static final int MOD = 1_000_000_007; MOD 1_000_000_007 private static final String YES = "Yes"; YES "Yes" private static final String NO = "No"; NO "No" public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        long N = sc.nextLong();

        System.out.println(solve(N));
    } main {
        Scanner sc = new Scanner(System.in);

        long N = sc.nextLong();

        System.out.println(solve(N));
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) long N = sc.nextLong(); N sc.nextLong() sc.nextLong sc System.out.println(solve(N)) System.out.println System.out System System.out solve(N) solve N String[] args args private static String solve(long N) {
        long[] num = new long[12+1];
        num[0] = 0;
        for (int i=1; i<12; i++) {
            num[i] = (long)Math.pow(26, i) + num[i-1];
            // System.err.println("i=" + i + " : " + num[i]);
        }



        StringBuilder ans = new StringBuilder();
        for (int i=1; i<=12; i++) {
            if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            }
        }

        return ans.reverse().toString();
    } solve {
        long[] num = new long[12+1];
        num[0] = 0;
        for (int i=1; i<12; i++) {
            num[i] = (long)Math.pow(26, i) + num[i-1];
            // System.err.println("i=" + i + " : " + num[i]);
        }



        StringBuilder ans = new StringBuilder();
        for (int i=1; i<=12; i++) {
            if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            }
        }

        return ans.reverse().toString();
    } long[] num = new long[12+1]; num new long[12+1] 12+1 12 1 num[0] = 0 num[0] num 0 0 for (int i=1; i<12; i++) {
            num[i] = (long)Math.pow(26, i) + num[i-1];
            // System.err.println("i=" + i + " : " + num[i]);
        } int i=1; int i=1; i 1 i<12 i 12 i++ i++ i {
            num[i] = (long)Math.pow(26, i) + num[i-1];
            // System.err.println("i=" + i + " : " + num[i]);
        } {
            num[i] = (long)Math.pow(26, i) + num[i-1];
            // System.err.println("i=" + i + " : " + num[i]);
        } num[i] = (long)Math.pow(26, i) + num[i-1] num[i] num i (long)Math.pow(26, i) + num[i-1] (long)Math.pow(26, i) Math.pow Math 26 i num[i-1] num i-1 i 1 StringBuilder ans = new StringBuilder(); ans new StringBuilder() for (int i=1; i<=12; i++) {
            if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            }
        } int i=1; int i=1; i 1 i<=12 i 12 i++ i++ i {
            if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            }
        } {
            if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            }
        } if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            } N <= num[i] N num[i] num i {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            } N -= num[i-1] + 1 N num[i-1] + 1 num[i-1] num i-1 i 1 1 for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                } int k=0; int k=0; k 0 k<i k i k++ k++ k {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                } {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                } int count = (int)(N%26); count (int)(N%26) N 26 ans.append((char)(count + 'a')) ans.append ans (char)(count + 'a') count 'a' N /= 26 N 26 break; return ans.reverse().toString(); ans.reverse().toString() ans.reverse().toString ans.reverse() ans.reverse ans long N N public class Main {
    private static final int MOD = 1_000_000_007;
    private static final String YES = "Yes";
    private static final String NO = "No";

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        long N = sc.nextLong();

        System.out.println(solve(N));
    }

    private static String solve(long N) {
        long[] num = new long[12+1];
        num[0] = 0;
        for (int i=1; i<12; i++) {
            num[i] = (long)Math.pow(26, i) + num[i-1];
            // System.err.println("i=" + i + " : " + num[i]);
        }



        StringBuilder ans = new StringBuilder();
        for (int i=1; i<=12; i++) {
            if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            }
        }

        return ans.reverse().toString();
    }
} public class Main {
    private static final int MOD = 1_000_000_007;
    private static final String YES = "Yes";
    private static final String NO = "No";

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        long N = sc.nextLong();

        System.out.println(solve(N));
    }

    private static String solve(long N) {
        long[] num = new long[12+1];
        num[0] = 0;
        for (int i=1; i<12; i++) {
            num[i] = (long)Math.pow(26, i) + num[i-1];
            // System.err.println("i=" + i + " : " + num[i]);
        }



        StringBuilder ans = new StringBuilder();
        for (int i=1; i<=12; i++) {
            if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            }
        }

        return ans.reverse().toString();
    }
} Main
import java.util.Scanner;

public class Main {
    private static final int MOD = 1_000_000_007;
    private static final String YES = "Yes";
    private static final String NO = "No";

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        long N = sc.nextLong();

        System.out.println(solve(N));
    }

    private static String solve(long N) {
        long[] num = new long[12+1];
        num[0] = 0;
        for (int i=1; i<12; i++) {
            num[i] = (long)Math.pow(26, i) + num[i-1];
            // System.err.println("i=" + i + " : " + num[i]);
        }



        StringBuilder ans = new StringBuilder();
        for (int i=1; i<=12; i++) {
            if (N <= num[i]) {
                // i文字
                N -= num[i-1] + 1;
                for (int k=0; k<i; k++) {
                    int count = (int)(N%26);
                    ans.append((char)(count + 'a'));
                    N /= 26;
                }

                break;
            }
        }

        return ans.reverse().toString();
    }
}