Spent a few hours today trying find the original title of a short story by Yasutaka Tsutsui (筒井 康隆), about a young matematician solving his problems with the help of Tokyo commuter trains. It was translated into Russian (two times) under the title "Кольцевые ветки". No amounts of Googling in 3 languages were able to find the desired data.

One of the clues is that the story supposedly came out in the collection "Vietnam Tourist Board" of 1967. The official site has a list of stories in the collection, but the titles do not seem to match (except, perhaps, "Trouble"/「トラブル」). So that was a dead end too.

UPDATE 2009/01/30: BluWacky of Cinnamon Ass e-mailed me that the title is "環状線" / "かんじょう せん" / "kanjou-sen", which directly means "Loop Lines" or "Circle Lines". It was published in 1968 in collection "アフリカの爆弾" (African Nuclear Bomb). Russian sources transliterate it as "Кандзё-сан", which made me think of it as a person's name and led me astray.

Sadly, there's no way to buy it, apparently. It's not in any of recent reprints of Mr. Tsutsui.

UPDATE: I've got it.