import std.stdio; import std.string; import std.conv; import std.algorithm; import std.range; import std.traits; import std.math; import std.conv; import std.typecons; import std.uni; import std.ascii; void main() { auto ip = readAs!(double[]), L = ip[0], K = ip[1]; (ceil(L / K / 2 - 1) * K).writeln; } // =================================== T readAs(T)() if (isBasicType!T) { return readln.chomp.to!T; } T readAs(T)() if (isArray!T) { return readln.split.to!T; } T[][] readMatrix(T)(uint height, uint width) if (isBasicType!T) { auto res = new T[][](height, width); foreach(i; 0..height) { res[i] = readAs!(T[]); } return res; } int ri() { return readAs!int; } string rs() { return readln.chomp; }