#include using namespace std;

int main() { int n, x, y; cin >> n >> x >> y;

// 向上取整公式：(y + x - 1) / x
int eat = (y + x - 1) / x;

// 剩余苹果不能小于0
int left = n - eat;
if (left < 0) left = 0;

cout << left << endl;
return 0;

}