680B - Bear and Finding Criminals

#include <iostream>

#include<vector>

#include<string>

#include<math.h>

#include<set>

#include<map>

#include<list>

#include<stack>

#include<queue>

#include <fstream>

#include<iterator>

#include<algorithm>

#include <iomanip>      // std::setprecision

/* ==================================================

  |                                                  |

  |    Author: *** S. M. Sabiul Hajjaj Sabit ***     |

  |       Last Edit:  May,14,2019                    |

   ================================================== */

///***global declaration***///

#define all(arr) arr.begin(),arr.end()

#define pb push_back

#define lb lower_bound

#define up upper_bound

#define sz(x) x.size()

#define min3(a,b,c)  min(min(a,b),c)

#define max3(a,b,c)  max(max(a,b),c)

#define lli long long int

using namespace std;

int i,j,n,m,sum=0,ans=0;

template <typename T>long long int power(T a, T b)

{

    long long int pow=1;

    for(int i=0; i<b; i++)

        pow *= a;

    return pow;

}

 

int main()

{

    int n,a;

    cin>>n>>a;

 

   int arr[200];

 

 

    for(int i=1; i<=n; i++)

    {

        cin>>arr[i];

    }

 

    int ans=0;

    if (arr[a]==1)

    {

        ans++;

    }

    int i=a-1;

    int j=a+1;

    while (i>=1&&j<=n)

    {

        if (arr[i]+arr[j]==2)ans+=2;

        i--;

        j++;

    }

    while (i>=1&&j>n)

    {

        if (arr[i])ans++;

        i--;

    }

    while (i<1&&j<=n)

    {

        if (arr[j])ans++;

        j++;

    }

    cout<<ans<<endl;

}