"use strict";
    
const main = arg => {
    arg = arg.trim().split("\n");
    let N = parseInt(arg[0].split(" ")[0]);
    const alphabets = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y", "z"];

    let temp = 0;
    let digit = 1;
    
    let list = [1];
    
    while(temp < N) {
        temp += Math.pow(26, digit);
        list.push(temp);
        digit++;
        console.log("temp;" + temp);
        console.log("digit;" + digit);
    }
    
    console.log("list:" + list);
    
    let result = [];
    
    // N = N - 26;
    
    let NC = list[list.length - 1] - list[list.length - 2];
    console.log(NC);
    
    console.log("---------")
    for(let i=1; i<digit; i++) {
        let num = Math.floor(NC / list[list.length - (i+1)]);
        //et num = Math.floor(NC / Math.pow(26, list[list.length - i]));
    
        result.push(alphabets[num]);
        
        NC = NC - (26 * num);
        
        console.log("i:" + i);
        console.log("num:" + num);
        console.log("NC:" + NC);
        console.log("-------------");
    }
    
    console.log(result.join(""));
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));