def max_non_overlapping_intervals(intervals):
    if not intervals:
        return 0
    
    intervals.sort(key=lambda x: x[1])
    
    count = 1
    end = intervals[0][1]
    
    for i in range(1, len(intervals)):
        if intervals[i][0] >= end:
            count += 1
            end = intervals[i][1]
    
    return count

# Пример использования
intervals = [(1, 3), (2, 4), (3, 6), (5, 7), (6, 8)]
print(max_non_overlapping_intervals(intervals))  # Вывод: 3