#include <bits/stdc++.h>
using namespace std;

typedef long double ld;

deque<ld> v;

vector<vector<ld>> dp;

ld chord(ld a){
  return (a-sinl(a))*0.5L;
}

// O(N^4)

int main(){
  int n; cin>>n;
  int m; cin>>m;
  v.resize(n); for (auto &i: v) cin>>i, i*=M_PI/180.L;

  ld best=0.L;

  for (int z=0; z<n; z++){
    v.push_back(v.front()+M_PI*2);

    dp.assign(n+1,vector<ld>(m+1));
    dp[0][0]=M_PI;

    for (int i=0; i<=n; i++){
      for (int j=0; j<m; j++){
        for (int k=i+1; k<=n; k++){
          //cerr<<" "<<i<<" "<<k<<" = "<<v[i]<<" "<<v[k]<<endl;
          dp[k][j+1]=max(dp[k][j+1],dp[i][j]-chord(v[k]-v[i]));
        }
      }
    }
    best=max(best,dp[n][m]);

    v.pop_front();
  }

  cout.precision(18);
  cout<<best*1000000<<endl;
}