# include <bits/stdc++.h>
# define speed ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
# pragma GCC optimize "-O3"
# define int long long
  
using namespace std;
  
const int N = 1e4 + 7;
const int mod = 1e9 + 7;

void solve() {
	int a, b, n;
	cin >> a >> b >> n;
	cout << (a*n) / b - a * (n / b) << '\n';
}

int32_t main() {
	speed;
	int T = 1;
	// cin >> T;
	while ( T-- ) {
		solve();
	}
}