Act as a certified physical therapist with 10 years of experience specializing in postural correction. Provide a detailed list of the [TOP 5 EXERCISES] to improve posture, specifically targeting [UPPER BACK, SHOULDERS, AND CORE]. For each exercise, include: 1) a step-by-step guide on proper form, 2) the recommended [NUMBER OF SETS AND REPS], and 3) common mistakes to avoid. Tailor the exercises for [OFFICE WORKERS] who sit for long hours, emphasizing quick routines that can be done at a desk or in small spaces. Explain how each exercise addresses specific postural issues like rounded shoulders or forward head posture.