FIBONACCI SERIES - IN LOGN TIME COMPLEXITY

Here, is code below to calculate nth term of Fibonacci series in log(n) time complexity. Do comment if find any bug. Thanks E-mail  :- surajjumpy@gmail.com

#include<iostream>

using namespace std;

void ope(int F[2][2], int M[2][2])
{
  int x =  F[0][0]*M[0][0] + F[0][1]*M[1][0];
  int y =  F[0][0]*M[0][1] + F[0][1]*M[1][1];
  int z =  F[1][0]*M[0][0] + F[1][1]*M[1][0];
  int w =  F[1][0]*M[0][1] + F[1][1]*M[1][1];

  F[0][0] = x;
  F[0][1] = y;
  F[1][0] = z;
  F[1][1] = w;
}

void mul(int M[2][2],int n)
{
    if(n <= 1)
        return;

    int F[2][2]={1,1,1,0};

    mul(M,n/2);

    ope(M,M);

    if(n&1)
        ope(M,F);
}

int fab(int n)
{
    if(n == 0)
        return 0;

    int M[2][2] = {1,1,1,0};

    mul(M,n-1);

    return M[0][0];
}

int main()
{
    int i;

    cout<<"Enter the term   no. ";
    cin>>i;

    cout<<"\nThe "<<i<<" term is    :   "<<fab(i);

    return 0;
}