[antlr-interest] How can I make sure there's one such rule in the input ?

[devdoer bird]

HI:

I have the grammar:

statements:(inputStatement|schemaStatement|filtersStatement|COMMENT)* EOF;


As you see ,it will match as many inputStatements as there are in the input
file.


How can change the grammar to  make sure there is only one inputStatment in
the input file?


Thanks.