user: Problem: Article: The Welshman is six seconds behind Quick-Step's Bob Jungels, the fourth man to lead the race, and four seconds ahead of fellow Briton Adam Yates.
Orica rider Yates was eighth on Tuesday's 181km stage, which finished on Mount Etna.
Slovenia's Jan Polanc, who rides for UAE Team Emirates, won the stage having broken away after just 2km.
Katusha's Ilnur Zakarin was second, 19 seconds back, before Thomas outsprinted FDJ's Thibaut Pinot.
Wednesday's stage takes the riders from Pedara to Messina, with the three-week race concluding in Milan on 28 May.
Team Sky's Geraint Thomas told BBC Wales Sport:
"There was a bit of a headwind in the last 2km so everyone was a bit of apprehensive. I felt good and obviously it was nice to win the sprint for the third [place] and get a few seconds as well.
"I felt pretty good on the climb but, with it being a headwind, everyone like myself didn't really want to go too early.
"I think everyone's still finding their legs and sussing each other out but a good start.
"It's a nice sort of psychological boost winning the sprint but there's still a long way to go until Milan [the final stage], and we'll know a lot more on Sunday."
Stage four result:
1.  Jan Polanc (Slo/UAE Team Emirates) 4hrs 55mins 58secs
2.  Ilnur Zakarin (Rus/Katusha) +19secs
3.  Geraint Thomas (GB/Team Sky) +29secs
4.  Thibaut Pinot (Fra/FDJ) Same time
5.  Dario Cataldo (Ita/Astana)
6.  Tom Dumoulin (Ned/Sunweb)
7.  Bob Jungels (Lux/Quick-Step)
8.  Adam Yates (GB/Orica)
9.  Bauke Mollema (Ned/Trek)
10. Vincenzo Nibali (Ita/Bahrain)
Overall classification after stage four
1.  Bob Jungels (Lux/Quick-Step) 19hrs 41mins 56secs
2.  Geraint Thomas (GB/Team Sky) +6secs
3.  Adam Yates (GB/Orica) +10secs
4.  Vincenzo Nibali (Ita/Bahrain) Same time
5.  Domenico Pozzovivo (Ita/AG2R)
6.  Nairo Quintana (Col/Movistar)
7.  Tom Dumoulin (Ned/Sunweb)
8.  Bauke Mollema (Ned/ Trek)
9.  Mikel Landa (Spa/Team Sky)
10. Thibaut Pinot (Fra/FDJ)
Answer: [[Team Sky's Geraint Thomas moved into second place in the Giro d'Italia by finishing third on stage four.]]

Problem: Article: On 9 September 2015 the Queen will have ruled for more than 63 years and 216 days.
She'll have overtaken the record set by her great-great-grandmother, Queen Victoria, more than a century ago.
The silver coin features the new picture of the Queen that was unveiled earlier this year.
Answer: [[A special £20 coin is being made to commemorate the Queen becoming Britain's longest reigning monarch.]]

Problem: Article: The 34-year-old former New Zealand international joined the Vikings from Hull FC in 2015 and has also played for New Zealand Warriors and Leigh.
"It was an easy decision to extend my time at the Vikings," he told the club website.
"My family and I love the town and I'm honoured to represent the club. I still feel that I have a lot to offer."
Answer: [[Widnes Vikings hooker Aaron Heremaia has signed a new one-year deal to keep him at the club for the 2018 season.]]

Problem: Article: Three of the 12 holes at Gogarburn Golf Club have been closed since Monday to allow police teams to search the area, following Saturday's discovery.
It is understood body parts were found in two different locations.
The initial find was in the grounds of Gogar Mount House and the other parts were later found a short distance away.
Dave Hamilton, Gogarburn Golf Club greens convenor, said he understood a caretaker at Gogar Mount House found a skull on Saturday and alerted the police.
He said: "On Monday morning detectives arrived and told us they had found a skull in the property next door to us and we knew nothing about it.
"We've closed the top field and we are playing a short course instead of the full course.
"We are helping the police in any way we can."
Police divers are searching ponds on the boundary of the golf course.
Answer:

assistant: [[Forensic experts are searching an Edinburgh golf course after human remains were found in the grounds of a nearby house.]]