#include <iostream>
#include <iomanip>
#include <vector>
#include <stdio.h>
#include <cstdlib>
#include <sstream>
using namespace std;

class BigNum {
public:
  BigNum() {
    buf_.push_back(0);
  }

  explicit BigNum(const string& s) {
    size_t i = s.size();
    while (i > 9) {
      buf_.push_back(stoul(s.substr(i - 9, 9)));
      i -= 9;
    }
    if (i > 0)
      buf_.push_back(stoul(s.substr(0, i)));

    if (!buf_.size())
      buf_.push_back(0);
  }

  BigNum(const BigNum& other) {
    buf_ = other.buf_;
  }

  BigNum& operator=(const BigNum& other) {
    buf_ = other.buf_;
    return *this;
  }

  friend BigNum operator*(const BigNum& a, const BigNum& b) {
    BigNum c("0");
    c.buf_.resize(0);
    c.buf_.resize(a.buf_.size() + b.buf_.size());

    for (size_t i = 0; i < a.buf_.size(); ++i)
      for (size_t j = 0, carry = 0;
           j < b.buf_.size() || carry;
           ++j) {
      carry += c.buf_[i + j];
      carry += a.buf_[i] * ((j < b.buf_.size()) ? b.buf_[j] : 0);

      c.buf_[i + j] = uint32_t(carry % a.BASE);
      carry /= a.BASE;
    }

    while (c.buf_.size() > 1 && c.buf_.back() == 0)
      c.buf_.pop_back();

    return c;
  }

  friend ostream& operator<<(ostream& os, const BigNum& a) {
    if (!a.buf_.size()) return os;
    os << a.buf_.back();
    for (auto it = ++a.buf_.rbegin();
         it != a.buf_.rend();
         ++it) {
      os << setfill('0') << setw(9) << *it;
    }

    return os;
  }
private:
  const uint32_t BASE = 1000000000;
  vector<uint32_t> buf_;
};

BigNum longFactorial(int N) {
  BigNum result("1");

  for (int i = 2; i <= N; i++) {
    result = result * BigNum(to_string(i));
  }
  return result;
}

int main() {   //факториал 100 (100!) на длинной арифметике
  BigNum fact = longFactorial(10);
  cout << fact << endl;
  system("PAUSE");
  return 0;
}