$$20$$ mL of calcium hydroxide was consumed when it was reacted with $$10$$ mL of unknown solution of H$$_2$$SO$$_4$$. Also $$20$$ mL standard solution of $$0.5$$ M HCl containing 2 drops of phenolphthalein was titrated with calcium hydroxide, the mixture showed pink colour when burette displayed the value of $$35.5$$ mL whereas the burette showed $$25.5$$ mL initially. The concentration of H$$_2$$SO$$_4$$ is _____ M. (Nearest integer)