#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ double a,b,c; cin>>a>>b; c=a-(int)(a/b)*b; cout<<fixed<<setprecision(2)<<c<<endl; return 0; }