If/else statement not working

Hi, I'm new at programming and I made this little program to test myself... but it didn't work! The problem seems to be at the end with the if/else statement. It always says "You're right!". Thanks in advance!

Code:

#include <iostream>

using namespace std;

int main()
{
    int a, b, c;
    struct gamelibrary {
           int gamecube;
           int playstation;
           int xbox;
           };
    gamelibrary john;
    cout<< "How many gamecube games does John have?\n";
    cin>> john.gamecube;
    cout<< "How many playstation games does John have?\n";
    cin>> john.playstation;
    cout<< "How many xbox games does John have?\n";
    cin>> john.xbox;
    cout<< "So John has "<< john.gamecube <<" gamecube games, right?\n";
    cout<< "1. Yes\n2. No\n";
    cin>> a;
    cin.get();
    if (a = 1){
          cout<< "You're right!";
          }
    else {
         cout<< "You're wrong!";
                }

    cin.get();
}

>> if (a = 1)

Two equals signs for comparison.

if(a == 1)
if(a == john.gamecube)