A numismatist Fred has some coins. A diameter of any coin is no more than 10 cm. All the coins are contained in a one-layer box of dimensions 30 cm by 70 cm. He is presented with a new coin. Its diameter is 25 cm. Prove that it is possible to put all the coins in a one-layer box of dimensions 55 cm by 55 cm.(Fedja Nazarov, St Petersburg) combinatoricscombinatorial geometry