#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
#include "bits/stdc++.h"
#include <ext/pb_ds/assoc_container.hpp>
#define all(a) a.begin() , a.end()
using namespace std;
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> indexed_set;
typedef tree<int,null_type,less_equal<int>,rb_tree_tag,tree_order_statistics_node_update>indexed_multiset;
void solve()
{
int n , k;
cin >> n >> k;
int b[n + 1] = {};
for(int i = 1 ; i <= n ; i++)
{
int a;
cin >> a;
b[i] = b[i - 1] + a;
}
int ans = 1000000000;
for(int i = 1 ; i <= n - k + 1; i++)
ans = min(ans , b[i + k] - b[i - 1] + 1);
cout << ans + (n - k);
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int t = 1;
//cin >> t;
while(t--)
solve();
}
