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

typedef long double ld;

deque<ld> v;

vector<vector<ld>> dp;

ld chord(ld u,ld v){
  if (u<v) u+=M_PI*2;
  ld const a=u-v;
  return (a-sinl(a))*0.5L;
}

// O(N^3)

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 w=1; w<=m;  w++){
      for (int i=w,j=w-1; i<=n; i++){
        while (j+1<i and w!=1 and dp[j  ][w-1]-chord(v[i],v[j  ])
                                < dp[j+1][w-1]-chord(v[i],v[j+1])){
          ++j;
        }
        dp[i][w]=max(dp[i][w],dp[j][w-1]-chord(v[i],v[j]));
      }
    }
    best=max(best,dp[n][m]);

    v.pop_front();
  }

  cout.precision(10);
  cout<<best*1000000<<endl;
}