#include <iostream>
#include <math.h>

using namespace std;

// 
// Code to convert a string read in from the command line to an int.
//
int main(int argc, char** argv)
{
  cout << endl;
  
  // This is for reading a value from the command line.
  // argc is the number of parameters passed to the program
  // including the command itself.  Therefore,  
  // StringToInt 123 will pass argc of 2 to main.
  if (argc != 2) {
	cout << "Usage: StringToInt int" << endl;
	exit(-1);
  }

  // Get the 1st parameter which should be the string to convert
  string myString = argv[1];

  int intValue = 0;

  // Iterate backwards so if the input string is "123"
  // i will be 2 then 1 then 0 and then the loop will break
  for (int i=myString.size() - 1;i>=0;i--) {

	// Get the ith character from the string and convert
	// from ascii by subtracting ascii '0' from the character.
	int digit    = myString[i] - '0';

	// Verify that the digit is between 0 and 9.  If not,
	// an invalid character was entered.
	if ( (digit < 0) || (digit > 9) ) { 
	  cerr << "The character " << myString[i] 
		   << " in the input string " << myString 
		   << " is not a numerical digit." << endl << endl;
	  exit(-1);
	}
	
	// We first add the 1's digit, then the 10's, then
	// the 100's, then the 1000's etc etc.  
	int exponent = myString.size() - 1 - i;

	// Add the digit times the multiplier which is
	// 10^exponent  (10 to the power exponent).
	intValue += pow(10,exponent) * digit;
  }
  
  cout << intValue << endl << endl;  // print out the result.
  
  return 0;  // Success!
}