Problem p02696 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;
// #pragma GCC optimize("Ofast")
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
#define REP(i, k, n) for (long long i = k; i < (long long)(n); i++)
#define all(a) a.begin(), a.end()
#define eb emplace_back
#define lb(v, k) (lower_bound(all(v), k) - v.begin())
#define ub(v, k) (upper_bound(all(v), k) - v.begin())
#define fi first
#define se second
#define pi M_PI
#define PQ(T) priority_queue<T>
#define SPQ(T) priority_queue<T, vector<T>, greater<T>>
using ll = long long;
using P = pair<ll, ll>;
using PP = tuple<ll, ll, ll>;
using S = multiset<ll>;
using vi = vector<ll>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
const ll inf = 1001001001001001;
const int INF = 1001001001;
const int mod = 1000000007;
const double eps = 1e-10;
template <class T> bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> void out(T a) { cout << a << '\n'; }
template <class T> void outp(T a) {
  cout << '(' << a.fi << ',' << a.se << ')' << '\n';
}
template <class T> void outvp(T v) {
  rep(i, v.size()) cout << '(' << v[i].fi << ',' << v[i].se << ')';
  cout << '\n';
}
template <class T> void outv(T v) {
  rep(i, v.size()) {
    if (i)
      cout << ' ';
    cout << v[i];
  }
  cout << '\n';
}
template <class T> void outvv(T v) { rep(i, v.size()) outv(v[i]); }
template <class T> bool isin(T x, T l, T r) { return (l) <= (x) && (x) <= (r); }
template <class T> void YesNo(T b) {
  if (b)
    out("Yes");
  else
    out("No");
}
void decimal(int x) { cout << fixed << setprecision(x); }
// ll GCD(ll a,ll b){if(b==0) return a; return GCD(b,a%b);}
// ll LCM(ll a,ll b){return(a/GCD(a,b))*(b/GCD(a,b))*GCD(a,b);}
ll POW(ll a, ll b) {
  a %= mod;
  if (b == 0)
    return 1;
  if (b & 1)
    return a * POW(a, b - 1) % mod;
  ll k = POW(a, b / 2);
  return k * k % mod;
}
vi calc(ll x) {
  vi res;
  while (x > 0) {
    res.eb(x % 10);
    x /= 10;
  }
  reverse(all(res));
  return res;
}

void solve() {
  ll a, b, n;
  cin >> a >> b >> n;
  ll ans = 0;
  REP(i, 1, min(b + 1, n + 1)) chmax(ans, (a * i) / b - a * (i / b));
  out(ans);
}

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  solve();
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
// #pragma GCC optimize("Ofast")
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
#define REP(i, k, n) for (long long i = k; i < (long long)(n); i++)
#define all(a) a.begin(), a.end()
#define eb emplace_back
#define lb(v, k) (lower_bound(all(v), k) - v.begin())
#define ub(v, k) (upper_bound(all(v), k) - v.begin())
#define fi first
#define se second
#define pi M_PI
#define PQ(T) priority_queue<T>
#define SPQ(T) priority_queue<T, vector<T>, greater<T>>
using ll = long long;
using P = pair<ll, ll>;
using PP = tuple<ll, ll, ll>;
using S = multiset<ll>;
using vi = vector<ll>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
const ll inf = 1001001001001001;
const int INF = 1001001001;
const int mod = 1000000007;
const double eps = 1e-10;
template <class T> bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> void out(T a) { cout << a << '\n'; }
template <class T> void outp(T a) {
  cout << '(' << a.fi << ',' << a.se << ')' << '\n';
}
template <class T> void outvp(T v) {
  rep(i, v.size()) cout << '(' << v[i].fi << ',' << v[i].se << ')';
  cout << '\n';
}
template <class T> void outv(T v) {
  rep(i, v.size()) {
    if (i)
      cout << ' ';
    cout << v[i];
  }
  cout << '\n';
}
template <class T> void outvv(T v) { rep(i, v.size()) outv(v[i]); }
template <class T> bool isin(T x, T l, T r) { return (l) <= (x) && (x) <= (r); }
template <class T> void YesNo(T b) {
  if (b)
    out("Yes");
  else
    out("No");
}
void decimal(int x) { cout << fixed << setprecision(x); }
// ll GCD(ll a,ll b){if(b==0) return a; return GCD(b,a%b);}
// ll LCM(ll a,ll b){return(a/GCD(a,b))*(b/GCD(a,b))*GCD(a,b);}
ll POW(ll a, ll b) {
  a %= mod;
  if (b == 0)
    return 1;
  if (b & 1)
    return a * POW(a, b - 1) % mod;
  ll k = POW(a, b / 2);
  return k * k % mod;
}
vi calc(ll x) {
  vi res;
  while (x > 0) {
    res.eb(x % 10);
    x /= 10;
  }
  reverse(all(res));
  return res;
}

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

signed main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  solve();
}