Codeforces 588B - Duff in Love

Duff in Love

Duff is in love with lovely numbers! A positive integer x is called lovely if and only if there is no such positive integer a > 1 such that a2 is a divisor of x.

Codeforces 287B - Pipeline

Pipeline

Vova, the Ultimate Thule new shaman, wants to build a pipeline. As there are exactly n houses in Ultimate Thule, Vova wants the city to have exactly n pipes, each such pipe should be connected to the water supply.

Codeforces 217A - Ice Skating

Ice Skating

Bajtek is learning to skate on ice. He’s a beginner, so his only mode of transportation is pushing off from a snow drift to the north, east, south or west and sliding until he lands in another snow drift. He has noticed that in this way it’s impossible to get from some snow drifts to some other by any sequence of moves. He now wants to heap up some additional snow drifts, so that he can get from any snow drift to any other one. He asked you to find the minimal number of snow drifts that need to be created.

Codeforces 92B - Binary Number

Binary Number

Little walrus Fangy loves math very much. That’s why when he is bored he plays with a number performing some operations.

UVA 100 - The 3n + 1 problem

The 3n + 1 problem

Problems in Computer Science are often classified as belonging to a certain class of problems (e.g.,NP, Unsolvable, Recursive). In this problem you will be analyzing a property of an algorithm whose classification is not known for all possible inputs.

Codeforces 221B - Little Elephant and Numbers

Little Elephant and Numbers

The Little Elephant loves numbers.

Codeforces 269A - Magical Boxes

Magical Boxes

Emuskald is a well-known illusionist. One of his trademark tricks involves a set of magical boxes. The essence of the trick is in packing the boxes inside other boxes.

Codeforces 298A - Snow Footprints

Snow Footprints

There is a straight snowy road, divided into n blocks. The blocks are numbered from 1 to n from left to right. If one moves from the i-th block to the (i + 1)-th block, he will leave a right footprint on the i-th block. Similarly, if one moves from the i-th block to the (i - 1)-th block, he will leave a left footprint on the i-th block. If there already is a footprint on the i-th block, the new footprint will cover the old one.

Codeforces 39H - Multiplication-Table

Multiplication-Table
Petya studies positional notations. He has already learned to add and subtract numbers in the systems of notations with different radices and has moved on to a more complicated action — multiplication. To multiply large numbers one has to learn the multiplication table. Unfortunately, in the second grade students learn only the multiplication table of decimals (and some students even learn it in the first grade). Help Petya make a multiplication table for numbers in the system of notations with the radix k.

Codeforces 1028C - Rectangles

Rectangles

You are given n rectangles on a plane with coordinates of their bottom left and upper right points. Some (n−1) of the given n rectangles have some common point. A point belongs to a rectangle if this point is strictly inside the rectangle or belongs to its boundary.