#include<iostream>
#include<stdio.h>
#include<algorithm>
#include <numeric> 
#include<math.h>
#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
// #include "boost/algorithm/string.hpp"
#define fio ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define mod 1000000007
#define mod1 mod
#define mod2 1000000007
#define ll long long int
#define ull unsigned long long int
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define readi(x) scanf("%d",&x)
#define  reads(x)  scanf("%s", x)
#define readl(x) scanf("%I64d",&x)
#define rep(i,n) for(i=0;i<n;i++)
#define revp(i,n) for(i=(n-1);i>=0;i--)
#define myrep1(i,a,b) for(i=a;i<=b;i++)
#define myrep2(i,a,b) for(i=b;i>=a;i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fi first
#define sec second
#define MAXN 1000000000000000005
#define MINN -1000000000000000000
#define INTMAX 1000001000
#define pii pair<ll,ll>
#define pdd pair<double,double>
#define pic pair<int,char>
#define lgn 20
#define ddouble long double
#define minus minu
#define PI 3.1415926535
#define lgn 20
#define coutd(x) cout << fixed << setprecision(x)
#define DECIMAL(n)  std::cout << std::fixed << std::setprecision(n); 
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define fil(v,x) fill(all(v),x)
#define filcon(v,x) iota(all(v),x)
#define newl '\n'
#define sz(x)       (int)x.size()
ull sqr(int x) { return 1ll * x * x; }

// #define INTMAX 200000000
 
// using namespace boost;
// #define si short int
 
using namespace std;
using namespace __gnu_pbds;
typedef priority_queue<ll, vector<ll > > max_pq;
typedef priority_queue<ll, vector<ll> , greater<ll>  > min_pq;
ll toint(const string &s) {stringstream ss; ss << s; ll x; ss >> x; return x;}
string tostring ( ll number ){stringstream ss; ss<< number; return ss.str();}
template<typename T>
T toIntegralType(const string &str) {
    static_assert(is_integral<T>::value, "Integral type required.");
    T ret;
    stringstream ss(str);
    ss >> ret;
    if ( to_string(ret) != str)
        throw invalid_argument("Can't convert " + str);
    return ret;
} 
// using namespace __gnu_pbds;
// typedef priority_queue<pair<ll,char> , vector<pair<ll , char> > > max_pq;
// typedef priority_queue<pii , vector<pii > ,greater<pii > > min_pq;
typedef tree<pii , null_type, less<pii>, rb_tree_tag, tree_order_statistics_node_update> OST;
// typedef priority_queue<pair < ll , pair < pii , ll > >  , vector<pair < ll , pair < pii , ll > >  > ,greater<pair < ll , pair < pii , ll > >  > > min_pq;
#define TRACE
#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
    template <typename Arg1>
    void __f(const char* name, Arg1&& arg1){
        cout << name << " : " << arg1 << std::endl;
        //use cerr if u want to display at the bottom
    }
    template <typename Arg1, typename... Args>
    void __f(const char* names, Arg1&& arg1, Args&&... args){
        const char* comma = strchr(names + 1, ','); cout.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...);
    }
#else
#define trace(...)
#endif
#define nn 2000005
bool isPowerOfTwo(ll n) 
{ 
   if(n==0) 
   return false; 
  
   return (ceil(log2(n)) == floor(log2(n))); 
} 
bool sortbysec(const pair<int,int> &a, 
              const pair<int,int> &b) 
{ 
    return (a.second < b.second); 
}
int psieve[1000005]={0};
void prime_sieve()
{
  //first mark all odd number prime
  for(int i=3;i<=1000000;i+=2)
  {
    psieve[i]=1;
  }

  //Sieve
  for(ll i=3;i<=1000000;i+=2)
  {
    // if the current number is not marked (it is prime)
    if(psieve[i]==1)
    {
      //mark all the multiples of i as not prime
      for(ll j=i*i; j<=1000000; j=j+i)
        psieve[j]=0;
    }
  }
  //special case
  psieve[2]=1;
  psieve[1]=psieve[0]=0;
}

int main()
{
   fio;
   // #ifndef ONLINE_JUDGE
   // freopen("input.txt","r",stdin);
   // freopen("output.txt","w",stdout);
   ll a,b,n,ans;
   cin>>a>>b>>n;
      if (n <= b - 1) {
        ans = floor(a * n / b);
    } else {
        ans = floor(a * (b - 1) / b);
    }
    cout << ans << endl;

}   



Measured memory_bytes: 3636