#include <bits/stdc++.h>
using namespace std;

typedef long long   signed int LL;
typedef long long unsigned int LU;

#define incID(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define incII(i, l, r) for(int i = (l)    ; i <= (r); i++)
#define decID(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define decII(i, l, r) for(int i = (r)    ; i >= (l); i--)
#define  inc(i, n) incID(i, 0, n)
#define inc1(i, n) incII(i, 1, n)
#define  dec(i, n) decID(i, 0, n)
#define dec1(i, n) decII(i, 1, n)

#define inII(v, l, r) ((l) <= (v) && (v) <= (r))
#define inID(v, l, r) ((l) <= (v) && (v) <  (r))

#define PB push_back
#define EB emplace_back
#define MP make_pair
#define FI first
#define SE second
#define PQ priority_queue

#define  ALL(v)  v.begin(),  v.end()
#define RALL(v) v.rbegin(), v.rend()
#define  FOR(it, v) for(auto it =  v.begin(); it !=  v.end(); ++it)
#define RFOR(it, v) for(auto it = v.rbegin(); it != v.rend(); ++it)

template<typename T> bool   setmin(T & a, T b) { if(b <  a) { a = b; return true; } else { return false; } }
template<typename T> bool   setmax(T & a, T b) { if(b >  a) { a = b; return true; } else { return false; } }
template<typename T> bool setmineq(T & a, T b) { if(b <= a) { a = b; return true; } else { return false; } }
template<typename T> bool setmaxeq(T & a, T b) { if(b >= a) { a = b; return true; } else { return false; } }
template<typename T> T gcd(T a, T b) { return (b == 0 ? a : gcd(b, a % b)); }
template<typename T> T lcm(T a, T b) { return a / gcd(a, b) * b; }

// ---- ----

const int D = 40;
struct StrInt {
	string s;
	void init(string t) {
		bool flag = (t[0] == '-');
		if(flag) { t = t.substr(1); }
		string u(D - t.size(), '0');
		s = u + t;
		if(flag) { (*this) = -(*this); }
	}
	void init(LL v) {
		init(tostr(v));
	}
	string tostr(LL x) {
		string s;
		bool f = (x < 0);
		if(f) { x *= -1; }
		while(x) {
			s.PB('0' + x % 10);
			x /= 10;
		}
		if(f) { s.PB('-'); }
		reverse(ALL(s));
		return s;
	}
	StrInt & operator++() {
		dec(i, D) {
			s[i]++;
			if(s[i] > '9') { s[i] = '0'; } else { break; }
		}
		return (*this);
	}
	StrInt & operator--() {
		dec(i, D) {
			s[i]--;
			if(s[i] < '0') { s[i] = '9'; } else { break; }
		}
		return (*this);
	}
	StrInt operator+() const {
		return (*this);
	}
	StrInt operator-() const {
		StrInt y;
		y.init(s);
		--y;
		inc(i, D) { y.s[i] = '0' + ('9' - y.s[i]); }
		return y;
	}
	StrInt operator+(const StrInt & x) {
		StrInt y = x;
		dec(i, D) {
			y.s[i] += (s[i] - '0');
			if(y.s[i] > '9') {
				y.s[i] -= 10;
				if(i != 0) { y.s[i - 1]++; }
			}
		}
		return y;
	}
	StrInt operator-(const StrInt & x) {
		return (*this) + (-x);
	}
	StrInt operator*(const StrInt & x) {
		StrInt y, z = x;
		y.init("0");
		dec(i, D) {
			inc(j, s[i] - '0') { y = y + z; }
			StrInt v = z;
			inc(j, 9) { z = z + v; }
		}
		return y;
	}
	bool operator<(const StrInt & x) const {
		bool f1 = (  s[0] < '5');
		bool f2 = (x.s[0] < '5');
		
		if(f1 == f2) { return (s < x.s); }
		if(! f1 &&   f2) { return true; }
		if(  f1 && ! f2) { return false; }
	}
	bool operator==(const StrInt & x) const {
		return s == x.s;
	}
};
ostream & operator<<(ostream & os, const StrInt & x) {
	StrInt s = x;
	if(s.s[0] >= '5') { s = -s; cout << "-"; }
	int p = D - 1;
	inc(i, D) {
		if(s.s[i] != '0') { p = i; break; }
	}
	os << s.s.substr(p);
	return os;
}

// ----

LL a, b, c;

bool f(LL x) {
	StrInt s, t, u;
	s.init(c - x - 1);
	t.init(x / a);
	u.init(b - 1);
	return (s < t * u);
}

int main() {
	cin >> a >> b >> c;
	
	LL l = 0, h = 1e18;
	while(h - l > 1) {
		LL m = (l + h) / 2;
		(f(m) ? h : l) = m;
	}
	cout << h << endl;
	
	return 0;
}