function alphabet(index, upper = false) {
    if (upper) {
        return String.fromCharCode('A'.charCodeAt(0) + index)
    }
    else {
        return String.fromCharCode('a'.charCodeAt(0) + index)
    }
}

function g(N) {
    if (N < 26) {
        return alphabet(N)
    }
    else {
        return g(Math.floor(N / 26) - 1) + alphabet(N % 26)
    }
}

function main(lines) {
    const [N] = parseNumberLine(lines[0])

    console.log(g(N - 1))
}

function parseNumberLine(line, radix = 10) {
    return line.split(/\s+/).map(_ => parseInt(_, radix))
}


main(require("fs").readFileSync("/dev/stdin", "utf8").split("\n"))
