Problem p02696 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <set>
#include <string>
#include <vector>
#pragma region Macros
#define int long long
#define double long double
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;
const int INF = 1e9;
#define krep(i, k, n) for (int i = (k); i < n + k; i++)
#define Krep(i, k, n) for (int i = (k); i < n; i++)
#define rep(i, n) for (int i = 0; i < n; i++)
#define rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define REP(i, n) for (int i = 1; i <= n; i++)
#define LAST(x) x[x.size() - 1]
#define ALL(x) (x).begin(), (x).end()
#define swap(a, b) (a += b, b = a - b, a -= b)
#define DIVCEIL(a, b) ((a + b - 1) / b)
#define SUM1n(n) ((n) * (n + 1) / 2)
#define SUMkn(k, n) (SUM1n(n) - SUM1n(k - 1))
// int CHMAX

int intpow(int a, int n) {
  // a^nのint ver
  if (n == 0)
    return 1;
  else {
    rep(i, n - 1) a *= a;
    return a;
  }
}
int MODPOW(int a, int n, int mod) {
  // a^n mod
  int ans = 1;
  while (n > 0) {
    if (n & 1)
      ans = ans * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return ans;
}
int FACT(int a) {
  if (a == 0)
    return 1;
  else
    return a * FACT(a - 1);
}
int MODFACT(int a, int mod) {
  int ans = 1;
  REP(i, a) {
    ans *= i;
    ans %= MOD;
  }
  return ans;
}
int nPr(int n, int r) {
  int s = n - r + 1;
  int sum = 1;
  for (int i = s; i <= n; i++)
    sum *= i;
  return sum;
}
int MODnPr(int n, int r, int mod) {
  int s = n - r + 1;
  int sum = 1;
  for (int i = s; i <= n; i++) {
    sum *= i;
    sum = sum % MOD;
  }
  return sum;
}
// int nCr(int n, int r)
int nCr2(int n, int r) { return FACT(n) / (FACT(r) * FACT(n - r)); }
int GCD(int a, int b) {
  if (a < b)
    swap(a, b);
  if (b == 0)
    return a;
  if (a % b == 0)
    return b;
  return GCD(b, a % b);
}
int LCM(int a, int b) { return a * b / GCD(a, b); }
int NUMOFDIV(int n) {
  // 約数の数（だっけ？）
  int ans = 0;
  REP(i, n) {
    if (n % i == 0)
      ans++;
  }
  return ans;
}
int CEIL1(int n) {
  // 1桁目切り上げ
  return (n + 9) / 10 * 10;
}
int GetDigit(int n) { return log10(n) + 1; }
int DIGIT(int n, int k) {
  // nのk桁目
  rep(i, k - 1) n /= 10;
  return n % 10;
}
int DIGITSUM(int n) {
  int sum = 0, dig;
  while (n) {
    dig = n % 10;
    sum += dig;
    n /= 10;
  }
  return sum;
}
int DIVTIME(int n, int k) {
  // nをkで何回割れるか的な
  int div = 0;
  while (n % k == 0) {
    div++;
    n /= k;
  }
  return div;
}
int binary(int n) {
  // 10進数→2進数
  int ans = 0;
  for (int i = 0; n > 0; i++) {
    ans += n % 2 * intpow(10, i);
    n /= 2;
  }
  return ans;
}
int intabs(int n) {
  if (n < 0)
    return -1 * n;
  else
    return n;
}
double LOG(int a, int b) { return log(b) / log(a); }
double DISTANCE(int x1, int y1, int x2, int y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
inline bool BETWEEN(int x, int min, int max) {
  if (min <= x && x <= max)
    return true;
  else
    return false;
}
inline bool between(int x, int min, int max) {
  if (min < x && x < max)
    return true;
  else
    return false;
}
inline bool PRIMEOR(int x) {
  if (x == 1)
    return false;
  if (x == 2)
    return true;
  if (x % 2 == 0)
    return false;
  double sqrtx = sqrt(x);
  for (int i = 3; i <= sqrtx; i += 2) {
    if (x % i == 0)
      return false;
  }
  return true;
}
bool SQRTOR(int n) {
  if (sqrt(n) == (int)sqrt(n))
    return true;
  else
    return false;
}
// 順位付け
using namespace std;
#pragma endregion

signed main() {
  int A, B, N;
  cin >> A >> B >> N;
  int ans = 0;
  rep(i, N + 1) {
    int x = floor((A * i) / B) - A * floor(i / B);
    ans = max(ans, x);
  }
  cout << ans;
}

Fixed submission:
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <set>
#include <string>
#include <vector>
#pragma region Macros
#define int long long
#define double long double
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;
const int INF = 1e9;
#define krep(i, k, n) for (int i = (k); i < n + k; i++)
#define Krep(i, k, n) for (int i = (k); i < n; i++)
#define rep(i, n) for (int i = 0; i < n; i++)
#define rrep(i, n) for (int i = n - 1; i >= 0; i--)
#define REP(i, n) for (int i = 1; i <= n; i++)
#define LAST(x) x[x.size() - 1]
#define ALL(x) (x).begin(), (x).end()
#define swap(a, b) (a += b, b = a - b, a -= b)
#define DIVCEIL(a, b) ((a + b - 1) / b)
#define SUM1n(n) ((n) * (n + 1) / 2)
#define SUMkn(k, n) (SUM1n(n) - SUM1n(k - 1))
// int CHMAX

int intpow(int a, int n) {
  // a^nのint ver
  if (n == 0)
    return 1;
  else {
    rep(i, n - 1) a *= a;
    return a;
  }
}
int MODPOW(int a, int n, int mod) {
  // a^n mod
  int ans = 1;
  while (n > 0) {
    if (n & 1)
      ans = ans * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return ans;
}
int FACT(int a) {
  if (a == 0)
    return 1;
  else
    return a * FACT(a - 1);
}
int MODFACT(int a, int mod) {
  int ans = 1;
  REP(i, a) {
    ans *= i;
    ans %= MOD;
  }
  return ans;
}
int nPr(int n, int r) {
  int s = n - r + 1;
  int sum = 1;
  for (int i = s; i <= n; i++)
    sum *= i;
  return sum;
}
int MODnPr(int n, int r, int mod) {
  int s = n - r + 1;
  int sum = 1;
  for (int i = s; i <= n; i++) {
    sum *= i;
    sum = sum % MOD;
  }
  return sum;
}
// int nCr(int n, int r)
int nCr2(int n, int r) { return FACT(n) / (FACT(r) * FACT(n - r)); }
int GCD(int a, int b) {
  if (a < b)
    swap(a, b);
  if (b == 0)
    return a;
  if (a % b == 0)
    return b;
  return GCD(b, a % b);
}
int LCM(int a, int b) { return a * b / GCD(a, b); }
int NUMOFDIV(int n) {
  // 約数の数（だっけ？）
  int ans = 0;
  REP(i, n) {
    if (n % i == 0)
      ans++;
  }
  return ans;
}
int CEIL1(int n) {
  // 1桁目切り上げ
  return (n + 9) / 10 * 10;
}
int GetDigit(int n) { return log10(n) + 1; }
int DIGIT(int n, int k) {
  // nのk桁目
  rep(i, k - 1) n /= 10;
  return n % 10;
}
int DIGITSUM(int n) {
  int sum = 0, dig;
  while (n) {
    dig = n % 10;
    sum += dig;
    n /= 10;
  }
  return sum;
}
int DIVTIME(int n, int k) {
  // nをkで何回割れるか的な
  int div = 0;
  while (n % k == 0) {
    div++;
    n /= k;
  }
  return div;
}
int binary(int n) {
  // 10進数→2進数
  int ans = 0;
  for (int i = 0; n > 0; i++) {
    ans += n % 2 * intpow(10, i);
    n /= 2;
  }
  return ans;
}
int intabs(int n) {
  if (n < 0)
    return -1 * n;
  else
    return n;
}
double LOG(int a, int b) { return log(b) / log(a); }
double DISTANCE(int x1, int y1, int x2, int y2) {
  return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}
inline bool BETWEEN(int x, int min, int max) {
  if (min <= x && x <= max)
    return true;
  else
    return false;
}
inline bool between(int x, int min, int max) {
  if (min < x && x < max)
    return true;
  else
    return false;
}
inline bool PRIMEOR(int x) {
  if (x == 1)
    return false;
  if (x == 2)
    return true;
  if (x % 2 == 0)
    return false;
  double sqrtx = sqrt(x);
  for (int i = 3; i <= sqrtx; i += 2) {
    if (x % i == 0)
      return false;
  }
  return true;
}
bool SQRTOR(int n) {
  if (sqrt(n) == (int)sqrt(n))
    return true;
  else
    return false;
}
// 順位付け
using namespace std;
#pragma endregion

signed main() {
  int A, B, N;
  cin >> A >> B >> N;
  int ans;
  if (N >= B - 1)
    ans = floor((A * (B - 1)) / B) - A * (floor((B - 1) / B));
  else
    ans = floor((A * (N)) / B) - A * (floor((N) / B));
  cout << ans;
}