function calka( a, b, n )

    local function f( x )
      return x^2 + 2*x;
    end

local h = ( b-a ) /n
local calka = 0

		for i = 1, n-1 do
			  calka = calka +  f( a + i/n  * (b-a) );
		end
		calka = calka + ( f( a ) + f( b )) / 2;
		calka = calka * h;

    print( "calka: "..calka );

end
calka( 1, 5, 444 )