#include <cstdio>

#include <cstdlib>

#include <cmath>

#include <cstring>

#include <time.h>

#include <string>

#include <set>

#include <map>

#include <list>

#include <stack>

#include <queue>

#include <vector>

#include <bitset>

#include <ext/rope>

#include <algorithm>

#include <iostream>

using namespace std;

#define ll long long

#define minv 1e-6

#define inf 1e9

//#define pi 3.1415926536

#define E  2.7182818284

const ll mod=1e9+;//

const int maxn=1e5+;

int main()

{

    int n,m;

    double pi=acos(-1.0);

    scanf("%d%d",&n,&m);

    printf("%.*f",m,pi*n);

    return ;

}