Problem:
Score : 400 points

Problem Statement

Given are integers A, B, and N.

Find the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-negative integer x not greater than N.

Here floor(t) denotes the greatest integer not greater than the real number t.

Constraints

1 ≤ A ≤ 10^{6}

1 ≤ B ≤ 10^{12}

1 ≤ N ≤ 10^{12}

All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B N

Output

Print the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-negative integer x not greater than N, as an integer.

Sample Input 1

5 7 4

Sample Output 1

2

When x=3, floor(Ax/B)-A×floor(x/B) = floor(15/7) - 5×floor(3/7) = 2. This is the maximum value possible.

Sample Input 2

11 10 9

Sample Output 2

9

Solution in C++ (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define pb push_back
#define mp make_pair
#define SZ(x) ((int)(x).size())
#define all(x) x.begin(),x.end()
#define mem0(s) memset(s,0,sizeof(s))
#define meminf(s) memset(s,0x3f,sizeof(s))
#define mp_insert(a,b,c) mp.insert(map<pair<int,int>,int>::value_type(make_pair(a,b),c))
double pi=acos(-1);
typedef long long ll;
typedef unsigned long long ull;
inline ll lowbit(ll x){return x&(-x);}
inline ll min(ll a,ll b){return a<b?a:b;}
inline ll max(ll a,ll b){return a>b?a:b;}
const ll INF=4223372036854775807,max_n=300005,mod=0x7f7f7f7f7f;
inline ll gcd(ll a,ll b){return b==0?a:gcd(b,a%b);}
inline ll pow(ll a,ll b,ll mod){ll res=1;a%=mod;assert(b>=0);for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
struct Node{int a,b,c,d;};Node data1[105];bool cmp(Node a,Node b){return a.d>b.d;}
int main()
{
	int a,b,n;cin>>a>>b>>n;
	if(n>=b)
	{
		//b-1;
		cout<<(a*(b-1))/b;
	}
	else
	{
		//n
		cout<<(a*n)/b;
	}

	return 0;
}