#include <iostream>
#include <math.h>

int main() {
  setlocale(LC_ALL, "Russian");
  double a = 0;
  double b = 0;
  double c = 0;
  double p = 0;
  std::cout << "Введите три стороны треугольника\n";
  std::cin >> a >> b >> c;
  if ((a == b) && (b == c)) {
    std::cout << "треугольник равносторонний\n";
  }

  if ((a == b) || (a == c) || (b == c)) {
    std::cout << "треугольник равнобедренный\n";
  }

  if ((a + b == c) && (a + c == b) && (b + c == a)) {
    std::cout << "треугольника не существует\n";
  } else {
    p = a + b + c;
  }
  double s = sqrt(p * (p - a) * (p - b) * (p - c));
  std::cout << "S = " << s << '\n';
}

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