#include #define rep(i,n) for(int i = 0; i < (n); ++i) #define srep(i,s,t) for (int i = s; i < t; ++i) #define drep(i,n) for(int i = (n)-1; i >= 0; --i) using namespace std; typedef long long int ll; typedef pair P; #define yn {puts("YES");}else{puts("NO");} #define MAX_N 200005 int main() { double a, b; cin >> a >> b; double ans = (b - a) * (b - a) * (b - a) / 6.0; cout << fixed << setprecision(10) << ans << endl; return 0; }