title: factorial of big numbers with strings in c++
body: <p>I am doing a factorial program with strings because i need the factorial of Numbers greater than 250</p>
  
  <p>I intent with:</p>
  
  <pre><code>string factorial(int n){
      string fact="1";
      for(int i=2; i&lt;=n; i++){
          b=atoi(fact)*n;
  
      }
  
  }
  </code></pre>
  
  <p>But the problem is that atoi not works. How can i convert my string in a integer.</p>
  
  <p>And  The most important Do I want to know if the program of this way will work with the factorial of 400 for example? </p>