function Main(input){
    input=input.split("\n");  //ここまで必須
    var alpha=new Array("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");

    var result="";
    while(input[0]>0){
        result=result+alpha[parseInt(input[0])%26-1];
        input[0]=Math.floor(parseInt(input[0])/26);
    }

    console.log(result);
}

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