unittest
{
	assert( [ "25" ].solve == "No" );
	assert( [ "30" ].solve == "Yes" );
}



import std.conv;
import std.range;
import std.stdio;

void main()
{
	stdin.byLineCopy.solve.writeln;
}

auto solve( Range )( Range input )
if( isInputRange!Range && is( ElementType!Range == string ) )
{
	auto x = input.front.to!( long );
	return ( 30 <= x ) ? "Yes" : "No";
}
