Fix typo in README

README.md

@@ -18,7 +18,7 @@ XOPP to OML converter
 
 Dependencies: Python3, Jinja2, xopp2py
 
-Entry point: xopp2oml.convert (Python script that takes as input as .xopp file and produces as output an .oml file)
+Entry point: xopp2oml.convert (Python script that takes as input a .xopp file and produces as output an .oml file)
 
 See also: [src/xopp2oml/README.md](src/xopp2oml/README.md)