#include<iostream>
#include<map>
#include<vector>

std::map<int, int> g_cyclicMap;

void InitCyclicNumbersMap(std::map<int, int>& cyclicMap)
{
    for (auto i = 0; i < 10; i++)
    {
        if ( (i < 2) || (i > 4 && i < 7) ) cyclicMap.insert(std::pair<int, int>(i, 1));
        else if ( (i > 1 && i < 4) || (i > 6 && i < 9) ) cyclicMap.insert(std::pair<int, int>(i, 4));
        else if ( (i == 4) || (i == 9) ) cyclicMap.insert(std::pair<int, int>(i, 2));
    }
}

int PowerLastDigit(long base, long power)
{
    int retValue;

    int baseUnitDigit = base % 10;
    int cyclicDigit = g_cyclicMap.at(baseUnitDigit);
    int reminder = power % cyclicDigit;

    if (cyclicDigit == 1)
    {
        retValue = baseUnitDigit;
    }
    else
    {
        retValue = pow<int>(baseUnitDigit, reminder);
    }

    return retValue;
}

int main()
{
    int result = 0;
    std::vector<int> input = { 5, 2, 4 };

    InitCyclicNumbersMap(g_cyclicMap);

    for (auto i = input.size() - 1; i > 0 ; i--)
    {
        auto base = input[i - 1];
        auto power = result;

        if (i == input.size() - 1)
        {
            power = input[i];
        }

        result = PowerLastDigit(base, power);
    }

    std::cout << "The last digit is: " << result;

    return 0;
}