What's wrong???

my code:

#include <cstdio>
#include <cmath>

int main() {
  int a, b, c, d;
  scanf("%d %d %d %d", &a, &b, &c, &d);

  if (a * b == c * d) {
    printf("Impossible.\n");
  } else {
    double cos = (a * a * 1.0 + b * b - c * c - d * d) / (2 * a * b - 2 * c * d);
    double x = a * a * 1.0 + b * b - 2 * a * b * cos;

    if (x < 0)
      printf("Impossible.\n");
    else
      printf("Distance is %d km.\n", (int)(sqrt(x) * 1000));
  }
}