LQB：Fibonacci数列

#include<iostream>
using namespace std; 
int main()
{
    unsigned long i=0,f1=1,f2=1,f3=1,n;    //1000000 用unsigned long；1000000000 用unsigned long long 
    cin>>n;
    if(n>2)
    for(i=3;i<=n;i++)
    {
         f3=(f2+f1)%10007;
         f1=f2;
         f2=f3;
     }
     cout<<f3;
     return 0;
 }