Problem p02696 (C++)

Buggy submission (status: Time Limit Exceeded):
// #include <bits/stdc++.h>
#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
// #include "boost/multiprecision/cpp_int.hpp"
// typedef boost::multiprecision::cpp_int LL;
typedef long double dd;
#define i_7 (ll)(1E9 + 7)
// #define i_7 998244353
#define i_5 i_7 - 2
ll mod(ll a) {
  ll c = a % i_7;
  if (c >= 0)
    return c;
  return c + i_7;
}
typedef pair<ll, ll> l_l;
typedef pair<dd, dd> d_d;
ll inf = (ll)1E16;
#define rep(i, l, r) for (ll i = l; i <= r; i++)
#define pb push_back
ll max(ll a, ll b) {
  if (a < b)
    return b;
  else
    return a;
}
ll min(ll a, ll b) {
  if (a > b)
    return b;
  else
    return a;
}
void Max(ll &pos, ll val) { pos = max(pos, val); } // Max(dp[n],dp[n-1]);
void Min(ll &pos, ll val) { pos = min(pos, val); }
void Add(ll &pos, ll val) { pos = mod(pos + val); }
dd EPS = 1E-9;
#define fastio                                                                 \
  ios::sync_with_stdio(false);                                                 \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define fi first
#define se second
#define endl "\n"
#define SORT(v) sort(v.begin(), v.end())
#define ERASE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define POSL(v, x) (lower_bound(v.begin(), v.end(), x) - v.begin())
#define POSU(v, x) (upper_bound(v.begin(), v.end(), x) - v.begin())
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

//////////////////////////

int main() {
  fastio ll a, b, n;
  cin >> a >> b >> n;
  ll ans = 0;
  if (b > n) {
    cout << a * n / b << endl;
    return 0;
  } else if (b <= 1000000) {
    rep(x, 0, n) { chmax(ans, a * x / b - a * (x / b)); }
  } else {
    ll x = b - 1;
    chmax(ans, a * x / b - a * (x / b));
  }
  cout << ans << endl;

  return 0;
}


Fixed submission:
// #include <bits/stdc++.h>
#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
// #include "boost/multiprecision/cpp_int.hpp"
// typedef boost::multiprecision::cpp_int LL;
typedef long double dd;
#define i_7 (ll)(1E9 + 7)
// #define i_7 998244353
#define i_5 i_7 - 2
ll mod(ll a) {
  ll c = a % i_7;
  if (c >= 0)
    return c;
  return c + i_7;
}
typedef pair<ll, ll> l_l;
typedef pair<dd, dd> d_d;
ll inf = (ll)1E16;
#define rep(i, l, r) for (ll i = l; i <= r; i++)
#define pb push_back
ll max(ll a, ll b) {
  if (a < b)
    return b;
  else
    return a;
}
ll min(ll a, ll b) {
  if (a > b)
    return b;
  else
    return a;
}
void Max(ll &pos, ll val) { pos = max(pos, val); } // Max(dp[n],dp[n-1]);
void Min(ll &pos, ll val) { pos = min(pos, val); }
void Add(ll &pos, ll val) { pos = mod(pos + val); }
dd EPS = 1E-9;
#define fastio                                                                 \
  ios::sync_with_stdio(false);                                                 \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define fi first
#define se second
#define endl "\n"
#define SORT(v) sort(v.begin(), v.end())
#define ERASE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define POSL(v, x) (lower_bound(v.begin(), v.end(), x) - v.begin())
#define POSU(v, x) (upper_bound(v.begin(), v.end(), x) - v.begin())
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}

//////////////////////////

int main() {
  fastio ll a, b, n;
  cin >> a >> b >> n;
  ll ans = 0;
  if (b > n) {
    cout << a * n / b << endl;
    return 0;
  } else if (b <= 1000000) {
    rep(x, 0, b) { chmax(ans, a * x / b - a * (x / b)); }
  } else {
    ll x = b - 1;
    chmax(ans, a * x / b - a * (x / b));
  }
  cout << ans << endl;

  return 0;
}