You are given a graph in anadjancencylistformat in a pickle file. Write a program (python3) todetermine the longest distance from node A of the graph.

Description You are given a graph in anadjancencylistformat in a pickle file. Write a program todetermine the longest distance from node 'A' of the graph. Input (From File: input.pkl) An adjacency list in a pickle file ('input.pkl') Ex: graph ={ 'A': ['B','C'], 'B': ['D','E'], 'C': ['F'], 'D': [], 'E':['G'], 'F':[], 'G': [] \} Output (To File: stdio.txt) Standard Output: an integer Ex: 3 Sample Input 1