#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n)for (int i = 0; i < int(n); ++i)
#define rrep(i,n)for (int i = int(n)-1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
template<class T> void chmax(T& a, const T& b) { a = max(a, b); }
template<class T> void chmin(T& a, const T& b) { a = min(a, b); }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using mint = modint998244353;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  ll a, b, n;
  cin >> a >> b >> n;
  if (a == 0 || a == b) {
    cout << 0 << '\n';
    return 0;
  }
  swap(a, b);
  ll c = a * a + b * b, d = a * a - b * b, g = gcd(c, d);
  ll m = d / g;
  ll t = c * m / d;
  ll dx = t * a, dy = t * b + m * b;
  if (max(dx, dy) >= n) {
    cout << 0 << '\n';
    return 0;
  }
  mint ans = mint(n - dx) * (n - dy) * 8;
  cout << ans.val() << '\n';
}