#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef pair<int,int> P;
constexpr int INF = 1e9;
int main(){
  double a, b;
  cin >> a >> b;
  int n = 100000;
  double h = (b - a) / n;
  double res = 0.0;
  for (int i = 0; i < n; i++) {
    double x1 = a + i * h, x2 = x1 + h;
    res += h / 2.0  * ((x1 - a) * (x1 - b) + (x2 - a) * (x2 - b));
  }
  printf("%.08f\n", abs(res));
  return 0;
}