unittest
{
	assert( [ "3 4 5" ].parse.expand.solve == 6 );
	assert( [ "5 12 13" ].parse.expand.solve == 30 );
	assert( [ "45 28 53" ].parse.expand.solve == 630 );
}



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

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

auto parse( Range )( Range input )
if( isInputRange!Range && is( ElementType!Range == string ) )
{
	auto abcs = input.front.split.to!( long[] );
	return tuple( abcs );
}

auto solve( long[] abcs )
{
	return abcs[ 0 ] * abcs[ 1 ] / 2;
}
