MINIMUM SIZE OF PLANETS

Chefu is an astronomer who observes planets every night. In a particular solar system, there are $N$ planets arranged in a row. Chefu is interested to note the planet with the smallest diameter, but he can only observe $K$ contiguous planets at a time due to its small telescope. So each day, he starts from the $i_{th}$ planet (initially $i$ is the first planet) and observes the next $K−1$ planets.