#include <cmath>
#include <cstdint>
#include <cstdlib>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>

struct Vector2D {
  int64_t x, y;
};

int main() {
  std::fstream input("input");
  std::string currentLine = "";
  std::vector<Vector2D> points{};
  int64_t password = 0;

  while (std::getline(input, currentLine, '\n')) {
    uint16_t positionOfTheComma = currentLine.find(',');
    points.push_back({std::stoll(currentLine.substr(0, positionOfTheComma)),
                      std::stoll(currentLine.substr(positionOfTheComma + 1))});
  }

  uint64_t count = 0, pointsSize = points.size();
  for (Vector2D &point : points) {
    for (uint64_t index = ++count; index < pointsSize; index++) {
      Vector2D *position1 = &point, *position2 = &points[index];
      int64_t area = (std::abs(position2->x - position1->x) + 1) *
                     (std::abs(position2->y - position1->y) + 1);
      if (area > password) {
        password = area;
      }
    }
  }
  std::cout << password << std::endl;
}