#pragma GCC optimize ("Ofast")
#include<bits/stdc++.h>
using namespace std;
inline int my_getchar_unlocked(){
  static char buf[1048576];
  static int s = 1048576;
  static int e = 1048576;
  if(s == e && e == 1048576){
    e = fread_unlocked(buf, 1, 1048576, stdin);
    s = 0;
  }
  if(s == e){
    return EOF;
  }
  return buf[s++];
}
inline void rd(double &x){
  int k;
  int m=0;
  int p=0;
  double r = 1;
  x = 0;
  for(;;){
    k = my_getchar_unlocked();
    if(k=='-'){
      m = 1;
      break;
    }
    if(k=='.'){
      p = 1;
      break;
    }
    if('0'<=k&&k<='9'){
      x = k - '0';
      break;
    }
  }
  for(;;){
    k = my_getchar_unlocked();
    if(k=='.'){
      p = 1;
      continue;
    }
    if(k<'0'||k>'9'){
      break;
    }
    if(p){
      r *= 0.1;
      x += r * (k - '0');
    }
    else{
      x = x * 10 + k - '0';
    }
  }
  if(m){
    x = -x;
  }
}
template<class T> inline T pow3_L(T a){
  return a*a*a;
}
int main(){
  double A;
  double B;
  double res;
  rd(A);
  rd(B);
  res = (pow3_L((B-A))) / 6.0;
  printf("%f\n",res);
  return 0;
}
// cLay varsion 20200317-1

// --- original code ---
// {
//   double A, B, res;
//   rd(A,B);
//   res = ((B-A) ** 3) / 6.0;
//   printf("%f\n",res);
// }