#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
	//输入用例 ：73.263 0.9973
	//预期输出结果：0.4601 
    double a, b, r;
    int k;
    cin >> a >> b;
    k = (int)(a/b);
    r = a - k * b;
    cout << r << endl;
    return 0;
}