#include<bits/stdc++.h>
#define int long long
#define pii pair<int,int>
#define fi first
#define se second
using namespace std;
using ll = long long;
using ldb = long double;
const int N = (int)1e8;
const int maxN = (int)1e6 + 1;
const int mod = 1e9 + 7;
void InputFile()
{
//freopen("scrivener.inp","r",stdin);
//freopen("scrivener.out","w",stdout);
//freopen("test.out","r",stdin);
}
void FastInput()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
}
int n,k;
int T[maxN];
vector<int> su;
int res = 0;
void Read()
{
cin >> n >> k;
for(int i = 1;i <= n;i++)
{
cin >> T[i];
if(i > 1)
{
res += T[i] - T[i-1];
su.push_back(T[i] - T[i-1]);
}
}
if(n == 1) {cout << 1;return;}
sort(su.begin(),su.end(),greater<int>());
for(int i = 0;i < k - 1;i++)
{
res -= su[i];
}
res += k;
cout << res;
}
void Solve()
{
}
void Debug()
{
//Main_sub();
//Naive();
}
int32_t main()
{
FastInput();
//InputFile();
//int sub_type;
//cin >> sub_type;
//Sieve();
int test;
//cin >> test;
test = 1;
while(test--)
//for(int prc = 1; prc <= test; prc++)
{
Read();
Solve();
//Debug();
}
}
