public static boolean isTransition(char s1, char s2){
		if ((s1=='A')&&(s2=='G')) return true;
		if ((s1=='G')&&(s2=='A')) return true;
		if ((s1=='C')&&(s2=='T')) return true;
		if ((s1=='T')&&(s2=='C')) return true;
		return false;
	}