#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

int a, b, N = 1000000;
double sum, pos;

int main() {
  cin >> a >> b;
  for (int i = 0; i < N; i++) {
    pos = (double)a + (double)(b - a) / N * i;
    sum += abs((pos - a) * (pos - b)) * (double)(b - a) / N;
  }
  cout << fixed << setprecision(15) << sum << endl;
  return 0;
}