51nod 1242 斐波那契数列的第N项

http://www.51nod.com/onlineJudge/questionCode.html#!problemId=1242

#include <cstdio>
typedef long long ll;
const int mod = 1e9+9;
struct Mat
{
    ll matrix[2][2];
};

Mat mul(Mat a,Mat b)
{
    Mat c;
    for(int i=0;i<2;i++)
        for(int j=0;j<2;j++)
        {
            c.matrix[i][j]=0;
            for(int k=0;k<2;k++)
            {
                c.matrix[i][j]+=(a.matrix[i][k]*b.matrix[k][j])%mod;
            }
            c.matrix[i][j]%=mod;
        }
    return c;
}
Mat mat;
Mat solve(ll m)
{
    Mat mt=mat;
    m--;
    while(m)
    {
        if(m&1)
        {
            mt=mul(mat,mt);
            m--;
        }
        mat=mul(mat,mat);
        m/=2;
    }
    return mt;
}
int main()
{
    //freopen("a.txt","r",stdin);
    ll n;
    scanf("%lld",&n);
    mat.matrix[0][0]=mat.matrix[0][1]=mat.matrix[1][0]=1;
    mat.matrix[1][1]=0;
    Mat c=solve(n-1);
    printf("%lld
",c.matrix[0][0]);
    return 0;
}