#include <bits/stdc++.h>
using namespace std;
namespace basic{
#define int long long
#define uint unsigned int
#define per(i,a,b) for(int i=(a);i<=(b);i++)
#define perr(i,a,b,c) for(int i=(a);i<=(b);i+=(c))
#define rep(i,b,a) for(int i=(b);i>=(a);i--)
#define epb emplace_back
#define bit(x) (1ll<<(x))
#define all(x,l,r) &(x)[l],&(x)[r]+1
#define vall(x) (x).begin(),(x).end()
#define lowbit(x) ((x)&(-(x)))
#define pc(x) putchar(x)
#define turn(x) (x-'a'+1)
#define cto const auto
template <class T> bool chkmn(T &x,T y){return x>y?(x=y,1):0;}
template <class T> bool chkmn(T &x,T y,T z){return y<z?(x=y,1):(x=z,0);}
template <class T> bool chkmx(T &x,T y){return x<y?(x=y,1):0;}
template <class T> bool chkmx(T &x,T y,T z){return y>z?(x=y,1):(x=z,0);}
char *p1,*p2,buf[100000];
#define nc() (p1==p2 && (p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++)
int read(){
    int x=0,f=1;char ch=nc();
    while(ch<48||ch>57){if(ch=='-') f=-1;ch=nc();}
    while(ch>=48&&ch<=57) x=x*10+ch-48,ch=nc();
    return x*f;
}
void write(int x){
    if(x<0) pc('-'),x=-x;
    if(x>9) write(x/10);
    pc(x%10+'0');
}
void print(string s,char op=0){for(auto x:s) pc(x);op&&pc(op);}
void print(int x,char op=0){write(x);op&&pc(op);}
}
using namespace basic;
namespace fisher{
bool mbe;void cntime();
const long double pi=acosl(-1);
int n,m,sum1,sum2,anspi,ansn;
long double ans;
void main(){
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    cin>>n>>m;
    if(m==1){
        per(i,1,n*2) ans+=i*(n*2-i+1);
        per(i,1,n) ans-=2*i;
    }
    else{
        per(i,1,n){
            sum1+=i*(2*n-2*i+1);
            sum2+=i*(2*i-1);
        }
        per(i,1,m-1){
            if(pi*i>2*m)
                ansn+=2*m*(sum1+sum2);
            else{
                ansn+=2*m*(sum2-sum1);
                anspi+=2*i*sum1;
            }
        }
        per(i,1,n*2) ansn+=m*i*(n*2-i+1);
        ans=anspi*pi+ansn;
    }
    cout<<fixed<<setprecision(10)<<ans<<'\n';
    return cntime();
}
bool mbd;void cntime(){
    cerr<<"Memory: "<<abs(&mbd-&mbe)/1048476.0<<" MB\n";
    cerr<<"Time: "<<1e3*clock()/CLOCKS_PER_SEC<<" ms\n";
}}
signed main(){
    fisher::main();
    return 0;
}