#include <bits/stdc++.h>
#include <cassert>
using namespace std;
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
#define pb push_back
#define ppb pop_back
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef pair<ll, ll> pl;
typedef vector<ll> vl;
typedef vector<vl> vvl;
#define rep2(i, n) for (ll i = 0; i < (n); ++i)
#define rep3(i, a, b) for (ll i = (a); i < (b); ++i)
#define rep_select(_1, _2, _3, name, ...) name
#define rep(...) rep_select(__VA_ARGS__, rep3, rep2)(__VA_ARGS__)
#define rrep2(i, n) for (ll i = (ll)(n) - 1; i >= 0; --i)
#define rrep3(i, a, b) for (ll i = (ll)(b) - 1; i >= (ll)(a); --i)
#define rrep(...) rep_select(__VA_ARGS__, rrep3, rrep2)(__VA_ARGS__)

int main(){
  ll h,w,m;
  cin >> h >> w >> m;
  assert(h%2==1&&w%2==1&&m==h*w-1);
  cout << -1 << endl;
}