error LNK2001: unresolved external symbol

[rpgplyrff8]

I have been working on this project for my C++ class that I am taking and Ive gotten an error message I have never seen before. When I am attempting to execute it i get the flowing error:

error LNK2001: unresolved external symbol "int __cdecl s(void)" (?s@@YAHXZ)

I have also posted my code following this. I would appreicate any help that is offered because I have no clue what is going on.

// Chapter 4 Project 20
// By William Creech

#include <iostream>
using namespace std;

int s (void);
int economy (void);

const int a = 10;
int aray [a] = {0};

int main ()
{
int cont = 0;
int c = 0;

while (cont =! -1)
cout << "Welcome to Creech Airlines.  Please enter \n 1 for 1st class \n 2 for Economy" << endl;
cin >> c;

switch (c)
{
	case 1:
		s ();
			break;
	case 2:
		economy ();
			break;
	default:
		cout << "Incorrect selection please enter the number again." << endl;
		cin >> c;
		break;
}
cout << "Are their more people in line?(enter -1 to end)" << endl;
cin >> cont;

return 0;

}

int s (int)
{

int x = 0;



	if ( aray [0] == 0)
	{
		aray [ 0 ] = 1;
		cout << "You are sitting in 1st class seat one.  Thank you, your flight will be leaving shortly." << endl;
	}
	else if ( aray [0] != 0)
	{
		aray [1] = 1;
		cout<< "You are sitting in 1st class seat two.  Thank you, your flight will be leaving shortly."  << endl;
	}
	else if (aray [1] != 0)
	{
		aray [2] = 1;
		cout << "You are sitting in 1st class seat three.  Thank you, your flight will be leaving shortly." << endl;
	}
	else if (aray [2] != 0)
	{
		aray[3] = 1;
		cout << "You are sitting in 1st class seat four. Thank you, your flight will be leaving shortly."  << endl;
	}
	else if (aray [3] != 0)
	{
		aray [4] = 1;
		cout << "You are sitting in 1st class seat five.  Thank you, your flight will be leaving shortly." << endl;
	}
	else 
	{
		cout << "There are no more 1st class seats available.  Is it ok to put you in economy class? (Press 1 for ok 2 for no)" << endl;
		cin >> x;
	}
		if ( x == 1)
			economy();
		else
			cout<< "The next flight will leave in three hours." << endl;
		
		
return 0;
}

int economy ()
{

int y = 0;

		if ( aray [5] == 0 )
	{
		aray [ 5 ] = 1;
		cout << "You are sitting in Economy class class seat one.  Thank you, your flight will be leaving shortly." << endl;
	}
	else if ( aray [5] != 0)
	{
		aray [6] = 1;
		cout<< "You are sitting in Economy class seat two.  Thank you, your flight will be leaving shortly."  << endl;
	}
	else if (aray [6] != 0)
	{
		aray [7] = 1;
		cout << "You are sitting in Economy class seat three.  Thank you, your flight will be leaving shortly." << endl;
	}
	else if (aray [7] != 0)
	{
		aray[8] = 1;
		cout << "You are sitting in Economy class seat four. Thank you, your flight will be leaving shortly."  << endl;
	}
	else if (aray [8] != 0)
	{
		aray [9] = 1;
		cout << "You are sitting in 1st class seat five.  Thank you, your flight will be leaving shortly." << endl;
	}
	else 
	{
		cout << "There are no more Economy class seats available.  Is it ok to put you in 1st class class? (Press 1 for ok 2 for no)" << endl;
		cin >> y;
	}
		if ( y == 1)
			s();
		else
			cout<< "The next flight will leave in three hours." << endl;
		
			return 0;
}

<< moderator edit: added [code][/code] tags >>

[Dave Sinkula]

Make sure your function's prototype matches its definition.

int s (void)