#include <cassert>
#include <cstdint>
#include <cstdlib>
#include <iostream>
#include <limits>

namespace checker {

std::string c_to_str(const int c) {
  if (c == '\n') {
    return "'\\n'";
  }
  if (c == std::char_traits<char>::eof()) {
    return "eof";
  }
  return std::string({'\'', char(c), '\''});
}

int scan_char() { return std::cin.get(); }
bool is_digit(const int c) { return '0' <= c && c <= '9'; }
int to_num(const int c) { return c - '0'; }

std::intmax_t scan_imax(const int end) {
  if (is_digit(end)) {
    std::cerr << "end must not be digit" << std::endl;
    std::abort();
  }
  std::intmax_t ret = 0;
  bool negative = false;
  int c = scan_char();
  if (c == '-') {
    negative = true;
    c = scan_char();
  }
  if (!is_digit(c)) {
    std::cerr << "no digits" << std::endl;
    std::abort();
  }
  if (c == '0') {
    if (negative) {
      std::cerr << "found -0" << std::endl;
      std::abort();
    }
    c = scan_char();
    if (is_digit(c)) {
      std::cerr << "leading zeros" << std::endl;
      std::abort();
    }
    if (c != end) {
      std::cerr << "expected " << c_to_str(end) << ", found " << c_to_str(c)
                << std::endl;
      std::abort();
    }
    return 0;
  }
  while (is_digit(c)) {
    c = to_num(c);
    if (ret > (std::numeric_limits<std::intmax_t>::max() - c) / 10) {
      std::cerr << "overflow" << std::endl;
      std::abort();
    }
    ret = ret * 10 + c;
    c = scan_char();
  };
  if (c != end) {
    std::cerr << "expected " << c_to_str(end) << ", found " << c_to_str(c)
              << std::endl;
    std::abort();
  }
  if (negative) {
    ret = -ret;
  }
  return ret;
}

constexpr int eof = std::char_traits<char>::eof();

void check() {
  int n = scan_imax('\n');
  assert(3 <= n && n <= 202020);
  assert(scan_char() == eof);
}

} // namespace checker

int main() {
  checker::check();
  return 0;
}