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

#define optimize()                \
    ios_base::sync_with_stdio(0); \
    cin.tie(0);                   \
    cout.tie(0);

typedef long long ll;
typedef double dl;

#define endl '\n'
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define nl cout << endl

ll ans = 0;
ll solve(int n, int m, int i)
{
    if(i > n) return 0;
    int temp; cin >> temp;
    solve(n, m, i+1);
    if(i >= m) ans += temp;
    return ans;
}
int main()
{
    optimize();
    
    int n, m;
    cin >> n >> m;
    ll res = solve(n, m, 1);
    cout << res << endl;

    return 0;
}