FRANKFURT, March 25 (JTA) — German police have arrested four teen-agers for giving the Nazi salute at the former concentration camp of Sachsenhausen. The teens later accosted a visitor who tried to photograph them. Police said the four came from the Berlin area. In February, employees at Sachsenhausen, located in eastern Germany, discovered right-wing slogans scrawled in the guest book of the memorial site. In 1992, an arson attack by right-wing extremists destroyed several of the barracks on the site. One barrack was reopened as a museum last year with an exhibition of objects that belonged to former prisoners.