import std.functional,
       std.algorithm,
       std.container,
       std.typetuple,
       std.typecons,
       std.bigint,
       std.string,
       std.traits,
       std.array,
       std.range,
       std.stdio,
       std.conv,
       std.format,
       std.math;

void main()
{
	auto r = readln.chomp.to!int;
	auto g = readln.chomp.to!int;
	writeln(2*g-r);
}