Problem p02696 (C++)

Buggy submission (status: Time Limit Exceeded):
/**
 * Created by hiramekun at 20:54 on 2020-05-02.
 */
#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using vb = vector<bool>;
using P = pair<ll, ll>;
template <typename T> using pq = priority_queue<T>;
template <typename T> using minpq = priority_queue<T, vector<T>, greater<T>>;
template <typename T, typename K> using ump = unordered_map<T, K>;
const ll dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const ll mod = 1000000007;
const ll inf = ll(1e9);
const ll e5 = ll(1e5);
const ll ll_inf = ll(1e9) * ll(1e9);

#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define repr(i, n) for (ll i = ll(n - 1); i >= 0; i--)
#define each(i, mp) for (auto &i : mp)
#define eb emplace_back
#define F first
#define S second
#define all(obj) (obj).begin(), (obj).end()

template <class T> ostream &operator<<(ostream &out, const vector<T> &list) {
  ll n = list.size();
  rep(i, n) out << list[i] << ' ';
  return out;
}

template <class T> istream &operator>>(istream &in, vector<T> &list) {
  ll n = list.size();
  rep(i, n) in >> list[i];
  return in;
}

template <class T>
ostream &operator<<(ostream &out, const vector<vector<T>> &list) {
  ll n = list.size();
  rep(i, n) out << list[i] << '\n';
  return out;
}

/* ------------- ANSWER ------------- */
/* ---------------------------------- */

void solve() {
  ll a, b, n;
  cin >> a >> b >> n;
  ll ans = -1;
  for (ll i = 1; i <= n; ++i) {
    ans = max(ans, (a * i) / b - a * (i / b));
  }
  cout << ans << '\n';
}

int main() {
#ifdef MY_DEBUG
  while (true) {
#endif
    solve();
#ifdef MY_DEBUG
  }
#endif
  return 0;
}

Fixed submission:
/**
 * Created by hiramekun at 20:54 on 2020-05-02.
 */
#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using vl = vector<ll>;
using vvl = vector<vl>;
using vb = vector<bool>;
using P = pair<ll, ll>;
template <typename T> using pq = priority_queue<T>;
template <typename T> using minpq = priority_queue<T, vector<T>, greater<T>>;
template <typename T, typename K> using ump = unordered_map<T, K>;
const ll dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
const ll mod = 1000000007;
const ll inf = ll(1e9);
const ll e5 = ll(1e5);
const ll ll_inf = ll(1e9) * ll(1e9);

#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define repr(i, n) for (ll i = ll(n - 1); i >= 0; i--)
#define each(i, mp) for (auto &i : mp)
#define eb emplace_back
#define F first
#define S second
#define all(obj) (obj).begin(), (obj).end()

template <class T> ostream &operator<<(ostream &out, const vector<T> &list) {
  ll n = list.size();
  rep(i, n) out << list[i] << ' ';
  return out;
}

template <class T> istream &operator>>(istream &in, vector<T> &list) {
  ll n = list.size();
  rep(i, n) in >> list[i];
  return in;
}

template <class T>
ostream &operator<<(ostream &out, const vector<vector<T>> &list) {
  ll n = list.size();
  rep(i, n) out << list[i] << '\n';
  return out;
}

/* ------------- ANSWER ------------- */
/* ---------------------------------- */

void solve() {
  ll a, b, n;
  cin >> a >> b >> n;
  if (n >= b - 1)
    cout << (a * (b - 1)) / b << '\n';
  else
    cout << a * (n) / b - a * (n / b) << '\n';
}

int main() {
#ifdef MY_DEBUG
  while (true) {
#endif
    solve();
#ifdef MY_DEBUG
  }
#endif
  return 0;
}