A practical introduction to Pascal programming language - GIARA

Iterative constructionsExercise 3.14. Write a program that reads from the user a sequence of integers ended by anynegative number. Then, counts how many times the sequence 1 2 3 occurs in non-consecutivepositions. That is, after a 1 all the values are ignored until a 2 occurs, and so on.□This program is conceptually more difficult than the previous, since we cannot store all theprevious value at each position of the sequence. So, instead of maintaing that, we will keep trackof the next expected value in the 1-2-3 subsequence. We do so by using the variable nowWaiting,which stores the next value we are waiting for in such subsequence. This variable is initialized to1, since that is the first value we are awaiting. Then, every time we were expecting (and found)a 3, we increase the counter and reset nowWaiting to 1.Program 53: Exercise 3.14program c03e14;vara:integer;nowWaiting:integer;counter:integer;beginwriteln(’Please input the sequence of integers ended by a negative: ’);counter:=0;nowWaiting:=1;repeat(* 1- Reading a new value *)read(a);(* 2- Updating the other variables *)if (nowWaiting=a) thenbeginnowWaiting:=nowWaiting+1;if (nowWaiting=4) thenbeginnowWaiting:=1;counter:=counter+1endenduntil(a