title: Project Euler #8, I don't understand where I'm going wrong
body: <p>I'm working on project <a href="https://projecteuler.net/problem=8" rel="nofollow noreferrer">euler problem number eight</a>, in which ive been supplied this ridiculously large number: </p>
  
  <p><code>7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450</code></p>
  
  <p>and am supposed to "Find the thirteen adjacent digits in the 1000-digit number that have the greatest product." EG the product of the first four adjacent digits is 7 * 3 * 1 * 6.
  My code is the following: </p>
  
  <pre><code>int main()
  {
      string num = /* ridiculously large number omitted */;
      int greatestProduct = 0;
      int product;
      for (int i=0; i &lt; num.length() -12; i++)
      {
          product = ((int) num[i] - 48);
          for (int j=i+1; j&lt;i+13; j++)
          {
              product = product * ((int) num[j] - 48);
              if (greatestProduct &lt;= product)
              {
                  greatestProduct = product;
              }
          }
      }
      cout &lt;&lt; greatestProduct &lt;&lt; endl;
  }
  </code></pre>
  
  <p>I keep getting 2091059712 as the answer which project euler informs me is wrong and I suspect its too large anyway. Any help would be appreciated.</p>
  
  <p>EDIT: changed to unsigned long int and it worked. Thanks everyone!</p>