I before E except after C

IbEeaC.cpp

#include <iostream>
#include <fstream>
#include <string>

bool IbEeaC(const std::string& word)
{
    for(auto position = word.find("ei"); position != std::string::npos; position = word.find("ei", position += 2))
    {
        if (position == 0 || word[position - 1] != 'c')
        {
            return false;
        }
    }

    return word.find("cie") == std::string::npos;
}

int main(int argc, char* argv[])
{
    if (argc < 2)
    {
        std::cout << "Please provide a parameter.\n"
            << "\tIbEeaC <word>\n"
            << "\tIbEeaC <filename>\n";

        return -1;
    }

    auto counter = 0u;
    const auto argument = std::string{ argv[1] };
    auto file = std::ifstream{ argument, std::ios_base::in };

    if (file.is_open())
    {
        for (auto word = std::string{}; std::getline(file, word);)
        {
            counter += IbEeaC(word);
        }
    }
    else
    {
        counter += IbEeaC(argument);
    }

    std::cout << counter << "\n";
}