#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

#define FOR(i, a, b) for (ll i = a; i <= (ll)(b); i++)

int main()
{
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  ll v, t, p;
  cin >> v >> t >> p;

  ll a = 0, i = 0, va = 0, vmax;
  vmax = (p + 1) * v;

  for (;;)
  {
    a += vmax/(t - 1)*t;
    i += vmax/(t - 1)*(t+1);

    if (a > vmax)
    {
      va = a - vmax;
      i -= va;
      a = vmax;
      break;
    }
  }

  cout << i << endl;

  return 0;
}