title: Finding the fibonacci number of large number
body: <p>I wrote the following program for finding the modulus of large Fibonacci's number. This can solve large numbers but fails to compute in cases like <code>fibo_dynamic(509618737,460201239,229176339)</code> where <code>a = 509618737</code>, <code>b = 460201239</code> and <code>N = 229176339</code>. Please help me to make this work.</p>
  
  <pre><code>long long  fibo_dynamic(long long  x,long long  y,long long  n, long long a[]){
      if(a[n]!=-1){
           return a[n];
      }else{
          if(n==0){
              a[n]=x;
              return x;
          }else if(n==1){
              a[n]=y;
              return y;
          }else {
              a[n]=fibo_dynamic(x,y,n-1,a)+fibo_dynamic(x,y,n-2,a);
              return a[n];
          }
      }
  }
  </code></pre>