FR 1644 then OS 769 at Vienna
Rome → Vienna → Varna
Timetable, Vienna time
21:30FR 1644 from Rome at the gate
12:30OS 769 to Varna leaves the gate
15 h apart on the timetable, overnight
OS 769 leaves 15 h after FR 1644 arrives on the timetable: more than half a day, so not a connection we count.