<tswett> learn \xd0\xa1\xd0\xa1\xd0\xa1\xd0\xa0 is the Russian way of writing USSR. They like to write U as \xd0\xa1 sometimes.

|a+b@| = { √(a²-b²) if a²-b² ≥ 0 ; i√(a²-b²) if a²-b² < 0 }