/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author Ido Kessler
 */

#include <iostream>

#include <fstream>
#include <vector>
#include <queue>
#include <sstream>
#include <algorithm>
#include <numeric>
#include <functional>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <bitset>
#include <iomanip>
#include <cstdint>
#include <cassert>

#include <tuple>
#include <math.h>

using ll = long long int;
using vi = std::vector<int>;
using vvi = std::vector<vi>;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using pi = std::pair<int, int>;
using vpi = std::vector<pi>;

#define all(x) (x).begin(), (x).end()
#define fori(i, n) for(int i = 0; i < n; i++)
#define rep(i, s, e) for(int i = (s); i <= (e); ++i)
#define repr(i, s, e) for(int i = (s); i >= (e); --i)
#define pb push_back

template<typename T> void mk_unique(T& l) { if (!std::is_sorted(all(l))) std::sort(all(l)); auto it = std::unique(l.begin(), l.end()); auto d = std::distance(l.begin(), it); l.resize(d); }
template<typename T> T &smax(T& l, const T&r) { if(l<r) l=r; return l; }
template<typename T> T &smin(T& l, const T&r) { if(l>r) l=r; return l; }

constexpr int MOD = 998244353;//1000000007;


namespace io{
class input_reader{
void throw_error(){throw std::runtime_error("No more inputs while reading number");}
template<typename T>
inline void readIntegerValue(T&f){bool positive=true;f=0;char c;
if(!in.get(c))throw_error();
while(c<'0'||c>'9'){if(c=='-')positive=false;if(!in.get(c))throw_error();}
while(c>='0'&&c<='9'){f=(f<<3)+(f<<1)+(c&15);if(!in.get(c))break;}
if(!positive)f*=-1;}
public:
std::istream&in;
explicit input_reader(std::istream&in):in(in){}
inline void read(int&f){readIntegerValue(f);}
inline void read(short&f){readIntegerValue(f);}
inline void read(long int&f){readIntegerValue(f);}
inline void read(long long int&f){readIntegerValue(f);}
inline void read(unsigned int&f){readIntegerValue(f);}
inline void read(unsigned short&f){readIntegerValue(f);}
inline void read(unsigned long int&f){readIntegerValue(f);}
inline void read(unsigned long long int&f){readIntegerValue(f);}
template<typename T>inline void read(std::vector<T>&f){for(auto&i:f)read(i);}
template<typename T,int N>inline void read(std::array<T,N>&res){for(auto&i:res)read(i);}
template<typename T1,typename T2>inline void read(std::pair<T1,T2>&p){read(p.first,p.second);}
template<typename T>inline void read(T&f){in>>f;}
template<typename T,typename...Args>inline void read(T&t,Args&...args){read(t),read(args...);}
template<typename T>inline void readArray(int n,T*res){while(n--)read(*(res++));}
template<typename T>inline input_reader&operator>>(T&t){return read(t),*this;}
};
}

namespace io{
class output_writer{
std::ostream&out;
template<typename T>inline void printIntegerHelper(T x){if(x>=10)printIntegerHelper(x/10);out.put(x%10+48);}
template<typename T>inline void printInteger(T x){if(x<0)out.put('-'),x=-x;printIntegerHelper(x);}
template<typename T>inline void printArray(T&ar){bool first=true;for(auto&t:ar)print((first)? first=false,"":" ",t);}
public:
explicit output_writer(std::ostream&out):out(out){}
inline void flush(){out.flush();}
inline void print(){}
inline void print(char x){out.put(x);}
inline void print(short x){printInteger(x);}
inline void print(int x){printInteger(x);}
inline void print(long int x){printInteger(x);}
inline void print(long long int x){printInteger(x);}
inline void print(unsigned short x){printInteger(x);}
inline void print(unsigned int x){printInteger(x);}
inline void print(unsigned long int x){printInteger(x);}
inline void print(unsigned long long int x){printInteger(x);}
template<typename T1>inline void print(const T1&t1){out<<t1;}
template<typename T1>inline void print(const std::vector<T1>&t1){printArray(t1);}
template<typename T1,int N>inline void print(const std::array<T1,N>&t1){printArray(t1);}
template<typename T1,int N,int M>inline void print(const std::array<std::array<T1,M>,N>&t1){for(auto&t:t1)println(t);}
template<typename T1>inline void print(const std::vector<std::vector<T1>>&t1){bool first=true;for(auto&t:t1)print((first)? first=false,"":"\n",t);}
template<typename T,typename...Args>inline void print(const T&t,Args...args){print(t),print(args...);}
template<typename...Args>inline void println(Args...args){print(args...),print('\n');}
template<typename T>output_writer&operator<<(const T&t){return print(t),*this;}
};
}

inline ll pow_mod(ll a,ll b,const ll MOD){ll res=1;for(ll i=1;b;b^=b&i,i<<=1,a=(a*a)%MOD)if(b&i)res=(res*a)%MOD;return res;}
inline ll mod_inv(const ll a,const ll MOD){return pow_mod(a,MOD-2,MOD);}
template<typename T>inline T gcd(T a,T b){T t;while(a!=0)t=a,a=b%a,b=t;return b;}
template<typename T>T lcm(const T &a,const T &b) {assert(a!=0&&b!=0);return a/gcd(a,b)*b;}
namespace math {
template<class T> int gMOD(T v){v%=MOD;if(v<0)v+=MOD;return (int)v;};
class mod_int{
using mi=mod_int;
int v;
public:
mod_int(int v):v(gMOD(v)){}
mod_int(unsigned int v):v(gMOD(v)){}
mod_int(long long int v):v(gMOD(v)){}
mod_int(unsigned long long int v):v(gMOD(v)){}
mod_int(long int v):v(gMOD(v)){}
mod_int(unsigned long int v):v(gMOD(v)){}
mod_int()=default;
mod_int(const mi& o)=default;
mod_int(mi&& o)=default;
inline mi& operator=(const mi& o)=default;
inline mi& operator=(mi&& o)=default;
inline mi& operator++(){if(v==MOD-1)v=0;else v++;return*this;}
inline mi& operator--(){if(v==0)v=MOD-1;else v--;return*this;}
inline mi operator++(int){mi t=*this;++(*this);return t;}
inline mi operator--(int){mi t=*this;--(*this);return t;}
inline bool friend operator==(const mi&lhs,const mi&rhs){return lhs.v==rhs.v;}
inline bool friend operator!=(const mi&lhs,const mi&rhs){return lhs.v!=rhs.v;}
template<typename T> inline bool friend operator==(const mi&lhs,const T&rhs){return lhs==mi(rhs);}
template<typename T> inline bool friend operator!=(const mi&lhs,const T&rhs){return lhs!=mi(rhs);}
inline mi friend operator-(const mi&lhs,const mi&rhs){mi res;res.v=lhs.v-rhs.v;if(res.v<0)res.v+=MOD;return res;}
inline mi friend operator+(const mi&lhs,const mi&rhs){mi res;res.v=lhs.v+rhs.v-MOD;if(res.v<0)res.v+=MOD;return res;}
inline mi friend operator*(const mi&lhs,const mi&rhs){return{((((long long int)lhs.v)*rhs.v))};}
inline mi friend operator/(const mi&lhs,const mi&rhs){return lhs*rhs.inv();}
template <typename T> inline mi friend operator-(const mi&lhs,const T&rhs){return lhs-mi(rhs);}
template <typename T> inline mi friend operator+(const mi&lhs,const T&rhs){return lhs+mi(rhs);}
template <typename T> inline mi friend operator*(const mi&lhs,const T&rhs){return lhs*mi(rhs);}
template <typename T> inline mi friend operator/(const mi&lhs,const T&rhs){return lhs/mi(rhs);}
template <typename T> inline mi& operator-=(const T&rhs){return*this=*this-rhs;}
template <typename T> inline mi& operator+=(const T&rhs){return*this=*this+rhs;}
template <typename T> inline mi& operator*=(const T&rhs){return*this=*this*rhs;}
template <typename T> inline mi& operator/=(const T&rhs){return*this=*this/rhs;}
inline mi inv()const{return pow(MOD-2);}
inline mi pow(long long int pw)const{mi res,val;res.v=1,val.v=v;while(pw){if(pw&1)res*=val;val*=val;pw>>=1;}return res;}
inline operator int()const {return v;}
inline friend std::istream& operator>>(std::istream& in,mi&rhs){long long int v;in>>v;rhs={v};return in;}
inline friend std::ostream& operator<<(std::ostream& out,mi&rhs){out<<rhs.v;return out;}
};
}
namespace math {
mod_int factorial(unsigned int n) {
static std::vector<mod_int> mem;static mod_int last;
if (mem.empty()) last = {1}, mem.push_back(last);
while (!(n < mem.size())) mem.push_back(mem.back() * last++);
return mem[n];
}
mod_int n_choose_k(int n, int k){
mod_int res =  factorial(n);mod_int res2 = (factorial(k) * factorial(n-k));
return res/res2;
}
}




template<typename P, typename CMP=std::less<P>, int B = 2>
class priority_queue_with_changes {
using K = int;
const CMP cmp = CMP();
public:
priority_queue_with_changes(int n) : index(n), pq(1) { assert(B > 1); }

struct state {K key;P priority;};
private:std::vector<int> index;std::vector<state> pq;
inline bool compare_indices(int i, int j) const { return cmp(pq[i].priority, pq[j].priority); }
void heap_up(int i) {const auto pme = pq[i];while (i >> B != 0) {__builtin_prefetch(&(*pq.begin()) + (i >> (B * 4)));
const auto pnxt = pq[i >> B];if (cmp(pnxt.priority, pme.priority)) {pq[i] = pnxt, index[pnxt.key] = i;i >>= B;
} else break;}pq[i] = pme, index[pme.key] = i;}

void heap_down(unsigned int i) {const auto pme = pq[i];const size_t len = pq.size();while ((i << B) < len) {
__builtin_prefetch(&(*pq.begin()) + (((size_t) i) << (4 * B)));auto p = pq[i << B];int inxt = i << B;
for (size_t j = 1; j < 1 << B && (i << B) + j < len; j++) {auto p1 = pq[(i << B) + j];
if (cmp(p.priority, p1.priority)) p = p1, inxt = (i << B) + j;}if (cmp(pme.priority, p.priority)) {
pq[i] = p, index[p.key] = i, i = inxt;} else break;}pq[i] = pme, index[pme.key] = i;}

public:bool was_poped(K key) const { return index[key] < 0; }
void push(K key, P priority) {int &i = index[key];if (i > 0) {P before = pq[i].priority;pq[i].priority = priority;
if (cmp(before, priority)) heap_up(i); else heap_down(i);}
else {i = pq.size();pq.push_back({key, priority});heap_up(i);}}

private:size_t get_index_of_max() const {size_t res = 1;for (size_t i = 2; i < (1 << B) && i < pq.size(); ++i)
if (cmp(pq[res].priority, pq[i].priority))res = i;
return res;}

public:const state &top() const {assert(!this->empty());return pq[get_index_of_max()];}
void pop() {assert(!this->empty());int i = get_index_of_max();K key = pq[i].key;index[key] = -1;
if (i == pq.size() - 1) pq.pop_back();else {pq[i] = pq.back(), index[pq[i].key] = i, pq.pop_back();heap_down(i);}}

class changable_entry {priority_queue_with_changes &pq;K k;public:
changable_entry(priority_queue_with_changes &pq_, K k_) : pq(pq_), k(k_) {}
operator P() {assert(pq.index[k] > 0);return pq.pq[pq.index[k]].priority;}
changable_entry &operator=(P p_) {pq.push(k, p_);return *this;}};

int count(K k) const { return index[k] > 0; }
changable_entry operator[](const K &k) { return changable_entry(*this, k); }
bool empty() const { return pq.size() == 1; }
};
//#include "points_query/point_query.hpp"
//#include "numeric/numeric.hpp"
//#include "hashes/hashes.hpp"
//#include "graphs/graphs.hpp"
//#include "geometry/geometry.hpp"
//#include "extension_operations/extensions.hpp"
//#include "ranges/ranges.hpp"

using mi = math::mod_int;
using vmi = std::vector<mi>;
using vvmi = std::vector<std::vector<mi>>;

using namespace std;

class DFloorFunction {
    class Solver {
    public:
        io::input_reader in;
        io::output_writer out;

        Solver(std::istream &in, std::ostream &out) : in(in), out(out) {}

        void print_case_number() {
            static int t = 0;
            // out <<"Case #" << ++t << ": ";
        }

        void solve() {
            print_case_number();
            // <code here>
            ll A, B, N;
            in.read(A, B, N);
            smin(N, B - 1);
            // </code here>
            out.println((A * N) / B - A * (N / B));
        }
    };

public:
    void solve(std::istream &in, std::ostream &out) {
        Solver(in, out).solve();
    }
};

int main() {
	std::ios_base::sync_with_stdio(false), cin.tie(0);
	DFloorFunction solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
	solver.solve(in, out);
	return 0;
}


Measured memory_bytes: 3656