Statement

Your ops channel has a running joke: "If at least 67% of devices are up, the network is vibing." You monitor a cluster of IoT devices for several minutes. For each minute, you know how many of the N devices reported as healthy. The team wants to find the first moment when the network becomes "vibing" and stays that way for K consecutive minutes. \medskip \noindentDefinition. Minute i is called good if at least 67% of devices are online at that minute: a_i * 100 > 67 * N where a_i is the number of online devices at minute i. \medskip \noindentTask. Given N, T, K, and the values a_1, a_2, …, a_T, find the earliest index i (1-based) such that minutes i, i+1, …, i+K-1 are all good. If no such i exists, output -1.