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 n = readln.chomp.to!int;
	int i = 1;
	while(true){
		if(n < i^^2) break;
		else i++;
	}
	writeln((i-1)^^2);
}