C++ optimized fib function via map

#include <iostream>
#include <map>

using namespace std;

map<int, unsigned long long> fibMap;
unsigned long long fibDemo4(int i);

int main()
{
    for (int i = 1; i < 50; i++)
    {
        cout << "i= " << i << ",fib result= " << fibDemo4(i)<< endl;
    }
    getchar();
}


unsigned long long fibDemo4(int i)
{
    map<int, unsigned long long>::iterator itr;
    itr = fibMap.find(i);
    if (itr!=fibMap.end())
    {
        return itr->second;
    }

    if (i == 1 || i==2)
    {
        if (i == 1)
        {
            fibMap.insert(pair<int, unsigned long long>(1, 1));
        }
        else
        {
            fibMap.insert(pair<int, unsigned long long>(2, 1));
        } 
        return 1;
    } 
    else 
    {
        unsigned long long result = fibDemo4(i - 2) + fibDemo4(i - 1);
        fibMap.insert(pair<int, unsigned long long>(i, result));
        return result;
    } 
}