A - kcal Editorial by en_translator


Since it is \(A/100\) kilocalories per one milliliters, the answer is \(AB / 100\). The following code (in C++) will be accepted:

#include <iostream>
using namespace std;

int main() {
  int A, B;
  cin >> A >> B;
  cout << A * B / 100.0 << '\n';
  return 0;
}

Here, if you express the operation of “dividing by 100” as A * B / 100, it will be rounded down since it is an integral operation. For example, 25 * 25 / 100 will be evaluated to 6, not 6.25. On the other hand, 100.0 is interpreted as a double type, so it will be processed as decimals.

One can explicitly cast to double type:

#include <iostream>
using namespace std;

int main() {
  int A, B;
  cin >> A >> B;
  cout << ((double) (A * B)) / 100 << '\n';
  return 0;
}

Note that although the code will be accepted under the constraints of the problem statement this time, if you feed \(A = 12345, B = 98765\) as an input, it will output 1.21925e+07. Accurate notation can be obtained with std::fixed or std::setprecision.

#include <iostream>
#include <iomanip>
using namespace std;

int main() {
  int A, B;
  cin >> A >> B;
  // std::fixed -> Instructs to output a fixed point decimal
  // std::setprecision(int n) -> Instructs to output n digits after the decimal point
  cout << fixed << setprecision(2);
  cout << A * B / 100.0 << '\n';
  return 0;
}

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