#include<iostream> #include<cstdio> //scanf()\printf() #include<cstring> #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ double a,b,c,d,e,ji; cin>>a>>b; c=a-(int) (a/b)*b; printf("%.2lf",c); return 0; }