Answer based on context:

After being blown out at home, the Steelers traveled to Kansas City to face the undefeated Chiefs. The Steelers scored first in the first quarter when Zach Fulton fumbled the ball into the end zone for a safety giving them a 2-0 lead. The Chiefs took the lead later on in the quarter when Harrison Butker kicked a 46-yard field goal to make it 3-2. The Steelers moved back ahead in the second quarter when Le'Veon Bell ran for a 3-yard touchdown making the score 9-3. This would be followed up by Chris Boswell kicking a 24-yard field goal to put the team up 12-3 at halftime. After a scoreless third quarter, the Chiefs came within 2 as Alex Smith connected with De'Anthony Thomas on a 57-yard pass to make it 12-10 to start the fourth quarter. Later on, the Steelers would move ahead by 9 when Ben Roethlisberger found Antonio Brown on a 51-yard pass to make it 19-10. The Chiefs came within 6 when Butker nailed a 33-yard field goal to make it 19-13. The Chiefs later on failed to convert a fourth down, sealing the win for the Steelers. With the win, the Steelers improved to 4-2. Roethlisberger's record against the Chiefs increased to 6-1.

How many passing touchdowns of at least 50 yards were completed?
2