import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv,
    std.functional, std.math, std.numeric, std.range, std.stdio, std.string,
    std.random, std.typecons, std.container;

ulong MAX = 100_100, MOD = 1_000_000_007, INF = 1_000_000_000_000;
alias sread = () => readln.chomp();
alias lread(T = long) = () => readln.chomp.to!(T);
alias aryread(T = long) = () => readln.split.to!(T[]);
alias Pair = Tuple!(string, "s", long, "p");
alias PQueue(T, alias less = "a>b") = BinaryHeap!(Array!T, less);

void main()
{
    auto n = lread();
    long eq = 1, ans;
    auto ary = iota(n / (eq + 1) + 1, n / eq).array();
    while (!ary.empty())
    {
        long ok = -1, ng = ary.length;
        while (abs(ok - ng) > 1)
        {
            auto mid = (ok + ng) / 2;
            if (n % ary[mid] >= eq)
                ok = mid;
            else
                ng = mid;
        }
        // ary.writeln();
        // ary[ok].writeln();
        // writefln("%s %s", ok, ng);
        if (ok < ary.length && n / ary[ok] == n % ary[ok])
            ans += ary[ok];

        eq++;
        ary = iota(n / (eq + 1) + 1, n / eq).array();
    }
    ans.writeln();
}

void scan(TList...)(ref TList Args)
{
    auto line = readln.split();
    foreach (i, T; TList)
    {
        T val = line[i].to!(T);
        Args[i] = val;
    }
}
