
    In a hospital's patient readmission database containing sorted patient identifiers, develop a function to identify the unique patient ID that appears only once, representing a non-recurring hospital visit. This analysis is crucial for studying patients with single admissions to understand factors that prevented readmission, while all other patients in the database have multiple recorded visits.
    

    
def search(arr):
    """
    In a hospital's patient readmission database containing sorted patient identifiers, develop a function to identify the unique patient ID that appears only once, representing a non-recurring hospital visit. This analysis is crucial for studying patients with single admissions to understand factors that prevented readmission, while all other patients in the database have multiple recorded visits.
    

    """
def search(arr):
    """
    In a hospital's patient readmission database containing sorted patient identifiers, develop a function to identify the unique patient ID that appears only once, representing a non-recurring hospital visit. This analysis is crucial for studying patients with single admissions to understand factors that prevented readmission, while all other patients in the database have multiple recorded visits.
    

    """
    n = len(arr)
    XOR = 0
    for i in range(n):
        XOR = XOR ^ arr[i]
    return XOR