premise: Gregory has only visited Andorra, Joel has only visited Federated States of Micronesia, Jimmy has only visited Niger, Darren has only visited Dominica, Ryan has only visited Suriname, Stephen has only visited Sudan, Ken has only visited Hungary, Theodore has only visited Mongolia, Jim has only visited Slovakia, Miguel has only visited Turkey, Herman has only visited Togo, Rafael has only visited Zambia
hypothesis: Ian didn't visit Niger