In this photo taken on Saturday, April 21, 2018, two Ukrainians fight against each other with wooden knives demonstrating their skills as the others watch, in a city park in Kiev, Ukraine. Schools of knife fight, members of which, all above 25 and do not take part in any competitions, have become particularly popular in Ukraine over the past few years. (AP Photo/Efrem Lukatsky)

In this photo taken on Saturday, April 21, 2018, two Ukrainians fight against each other with wooden knives demonstrating their skills as the others watch waiting for their turn, in a city park in Kiev, Ukraine. Schools of knife fight, members of which, all above 25 and do not take part in any competitions, have become particularly popular in Ukraine over the past few years. (AP Photo/Efrem Lukatsky)

In this photo taken on Saturday, April 21, 2018, two Ukrainians fight against each other with wooden knives demonstrating their skills as the others watch waiting for their turn, in a city park in Kiev, Ukraine. Schools of knife fight, members of which, all above 25 and do not take part in any competitions, have become particularly popular in Ukraine over the past few years. (AP Photo/Efrem Lukatsky)

In this photo taken on Saturday, April 21, 2018, two Ukrainians fight against each other with wooden knives demonstrating their skills as the others watch waiting for their turn, in a city park in Kiev, Ukraine. Schools of knife fight, members of which, all above 25 and do not make part in any competitions, have become particularly popular in Ukraine over the past few years. (AP Photo/Efrem Lukatsky)

In this photo taken on Saturday, April 21, 2018, two Ukrainians fight against each other with wooden knives demonstrating their skills as the others watch waiting for their turn, in a city park in Kiev, Ukraine. Schools of knife fight, members of which, all above 25 and do not take part in any competitions, have become particularly popular in Ukraine over the past few years. (AP Photo/Efrem Lukatsky)

In this photo taken on Saturday, April 21, 2018, a Ukrainian fights against his opponent, unseen, with a wooden knife demonstrating his skills in a city park in Kiev, Ukraine. Schools of knife fight, members of which, all above 25, do not make part in any competitions, have become particularly popular in Ukraine over the past few years. (AP Photo/Efrem Lukatsky)

In this photo taken on Saturday, April 21, 2018, a Ukrainian fights against his opponent, unseen, with a wooden knife demonstrating his skills in a city park in Kiev, Ukraine. Schools of knife fight, members of which, all above 25, do not make part in any competitions, have become particularly popular in Ukraine over the few past years. (AP Photo/Efrem Lukatsky)

In this photo taken on Saturday, April 21, 2018, two Ukrainians fight against each other with wooden knives demonstrating their skills as the others watch waiting for their turn, in a city park in Kiev, Ukraine. Schools of knife fight, members of which, all above 25, do not make part in any competitions, have become particularly popular in Ukraine over the past few years. (AP Photo/Efrem Lukatsky)