mplement the function fileSum. fileSum is passed in a name of a file. This function should open the file, sum all of the integers within this file, close the file, and then return the sum. If the file does not exist, this function should output an error message and then call the exit function to exit the program with an error value of 1.Please Use This Code Template To Answer the Question#include #include #include //needed for exit functionusing namespace std;// Place fileSum prototype (declaration) hereint main() {string filename;cout << "Enter the name of the input file: ";cin >> filename;cout << "Sum: " << fileSum(filename) << endl;return 0;}// Place fileSum implementation here