Clear the Multiset

You have a multiset containing several integers. Initially, it contains $$$a_1$$$ elements equal to $$$1$$$, $$$a_2$$$ elements equal to $$$2$$$, ..., $$$a_n$$$ elements equal to $$$n$$$.

You may apply two types of operations:

• choose two integers $$$l$$$ and $$$r$$$ ($$$l \le r$$$), then remove one occurrence of $$$l$$$, one occurrence of $$$l + 1$$$, ..., one occurrence of $$$r$$$ from the multiset. This operation can be applied only if each number from $$$l$$$ to $$$r$$$ occurs at least once in the multiset;
• choose two integers $$$i$$$ and $$$x$$$ ($$$x \ge 1$$$), then remove $$$x$$$ occurrences of $$$i$$$ from the multiset. This operation can be applied only if the multiset contains at least $$$x$$$ occurrences of $$$i$$$.

What is the minimum number of operations required to delete all elements from the multiset?