Runtime Error while building a decryption program.

Here i'm building a decryption program and a runtime error occurs when actually running it from powershell and passing a file as an argument and an output file name.

Error: This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information.

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

const std::string &SALT1 = "LM::TB::BB";
const std::string &SALT2 = "__:/__77";
const std::string &SALT3 = "line=wowC++";
const std::string &BASE64_CODES = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

std::string DecryptB64 (std::string s);
std::string base64_decode(const std::string &s);

int main(int argc, char *argv[])
{
    if(argc != 3)
        return std::cout<< "Program needs Two Arguments, input and output" <<std::endl, 2;
    std::string in (argv[1]), out (argv[2]);
    std::ifstream fi (in);
    if (!fi)
        return std::cout << "Cannot read input file '" << in << "'" << std::endl, 3;
    std::string data;
    fi >> data;
    if (!fi)
        return std::cout << "Input file '" << in << "' corrupted!" << std::endl, 4;
    data = DecryptB64(data);
    std::ofstream fo (out);
    if (!fo)
        return std::cout << "Cannot write output file '" << out << "'" << std::endl, 5;
    fo << data;
    std::cout << "Decoding was successful" << std::endl;
    return 0;
}

std::string base64_decode(const std::string &s)
{
    std::string ret;
    std::vector<int> vec(256, -1);
    for (int i = 0; i < 64; i++)
        vec [BASE64_CODES[i]] = i;
    int val = 0, bits = -8;
    for (const auto &c : s)
        {
            if (vec[c] == -1) break;
            val = (val << 6) + vec[c];
            bits += 6;

            if (bits >= 0)
                {

                    ret.push_back(char((val >> bits) & 0xFF));
                    bits -= 8;
                }
        }

    return ret;
}

std::string DecryptB64 (std::string s)
{
    s = s.erase (7, 1);
    s = s.erase (1, 1);
    s = base64_decode (s);
    s = s.substr (SALT2.length() + SALT3.length());
    s = s.substr (0, s.length() - SALT1.length());
    s = base64_decode (s);
    s = s.substr (0, s.length() - SALT1.length());
    s = s.erase (7, SALT3.length());
    s = base64_decode (s);
    s = s.substr (SALT1.length());
    s = s.substr (0, s.length() - SALT2.length() - SALT3.length());
    return s;
}