#include <cstdint>
#include <fstream>
#include <iostream>
#include <map>
#include <string>

typedef uint64_t inclusiveLowerBound;
typedef uint64_t inclusiveUpperBound;

int main() {
  std::fstream input("input");
  std::string currentLine = "";
  std::multimap<inclusiveLowerBound, inclusiveUpperBound> ranges{};
  uint16_t positionOfHypen = 0;
  uint64_t upperBound = 0, lowerBound = 0;

  // Range and values are seperated by an empty \n
  while (std::getline(input, currentLine, '\n')) {
    if (currentLine == "") {
      break;
    }

    positionOfHypen = currentLine.find('-');
    lowerBound = std::stoull(currentLine.substr(0, positionOfHypen));
    upperBound = std::stoull(currentLine.substr(positionOfHypen + 1));

    ranges.insert({lowerBound, upperBound});
  }

  // First time doing this with ranges
  auto range = ranges.begin();
  while (range != ranges.end()) {
    auto secondRange = range;
    secondRange++;

    while (secondRange != ranges.end()) {
      // 3 Possible cases

      bool isEndOfFirstBiggerThanSecond = range->second >= secondRange->second;
      // 1. Second range is fully inside First range
      if (isEndOfFirstBiggerThanSecond) {
        secondRange = ranges.erase(secondRange);
        continue;
      }

      // 2. Second Range's end is bigger than first, but Second's start is
      // smaller than first's end
      if (!isEndOfFirstBiggerThanSecond &&
          range->second >= secondRange->first) {
        range->second = secondRange->second;
        secondRange = ranges.erase(secondRange);
        continue;
      }

      // 3. Nothing happens, they are not overlapping
      secondRange++;

      // Note: The begining of first range WILL ALWAYS be smaller than second
    }
    range++;
  }

  uint64_t password = 0;
  for (auto keys : ranges) {
    password += keys.second - keys.first + 1; // 1 is for range to be inclusive
  }
  std::cout << password << std::endl;

  return 0;
}