Expected points per minute

For every open problem, estimate: P(full solve) x full points vs P(subtask) x partial points, divided by the minutes each needs. Submit the best ratio first. A 40-point subtask at minute 40 usually beats a 100-point gamble at minute 150.

Keep every partial-score opportunity alive: constraints listed in the statement ARE the subtask map. n <= 1000 means the O(n^2) writer is being invited. Two independent constraints usually mean two independent partial solutions.