Recomm. for undergrads: yes |

Prize: Ł10 |

Posted | by: | tigris35711 |

on: | December 25th, 2012 |

* indicates original appearance(s) of problem.

- Subject
- Algebra (6)
- Analysis (5)
- Combinatorics (36)
- Geometry (28)
- Graph Theory (224)
- Group Theory (5)
- Logic (10)
- Number Theory (47)
- Theoretical Comp. Sci. (13)
- Topology (39)
- Unsorted (1)

- Author index
- Keyword index

## Solution

It's a simple application of the Shwartz inequality:

Shwartz: because is a partition of .