import core.bitop, std.bitmanip;
import core.checkedint;
import std.algorithm, std.functional, std.meta;
import std.array, std.container;
import std.bigint;
import std.conv;
import std.math, std.numeric;
import std.range, std.range.interfaces;
import std.stdio, std.string;
import std.ascii, std.typecons;

void main()
{
    long n;
    readf("%s", &n);
    readln;

    const int BASE = 26;
    
    long high = 1;
    while (n > high * BASE) {
        high *= BASE;
        n -= high;
    }
    
    n -= 1;
    
    char[] ans;
    while (high > 0) {
        int cur = (n / high).to!int;
        
        ans ~= ('a' + cur);
        
        n -= cur * high;
        high /= BASE;
    }
    
    ans.writeln;
}