Concise tutorials on algorithms, data structures, and competitive-programming techniques.
To use Python in competitive programming, you will have to know how to take input from stdin.
If you are given a number N, you have to determine how many integers between 1 and N have a GCD of 1 with N.
A beginner's number theory tutorial on Sieve of Eratosthenes.
Default I/O is sometimes too slow for large data. Use buffered reads/writes or fast parsers to avoid timeouts.
