function Main(input) {
    var N = parseInt(input.trim(),10);
    var abc = 'abcdefghijklmnopqrstuvwxyz';
    var x = 0;
    var sum = 0;
    var ary_ans = [];
    var str;
    checkXmax_loop:
    while (true){
        if (N > (sum + Math.pow(26, (x+1)))){
          	sum += Math.pow(26, (x+1));
            x++;
        } else {
            break checkXmax_loop;
        }
    }
    N -= (sum + 1);

    for (var i = x; i > 0; i--){
        str = abc.substr(Math.floor(N / Math.pow(26, i)) , 1);
        ary_ans.push(str);
        N -=  (Math.floor(N / Math.pow(26, i))* Math.pow(26, i));
    }
    ary_ans.push(abc.substr(N, 1));           
    console.log(ary_ans.join(''));
}   


Main(require("fs").readFileSync("/dev/stdin", "utf8"));