premise: Guy has only visited Costa Rica, William has only visited Poland, Clifford has only visited Italy, Byron has only visited Gabon, Tom has only visited Dominica, Pedro has only visited São Tomé & Prícipe, Bernard has only visited Tuvalu, Javier has only visited Mongolia, Gregory has only visited Saint Kitts & Nevis, Melvin has only visited Saudi Arabia, Bob has only visited Djibouti
hypothesis: Stephen didn't visit Italy