#include <bits/stdc++.h>
using namespace std;
inline void setup()
{
#ifndef ONLINE_JUDGE
freopen("test.inp", "r", stdin);
freopen("test.out", "w", stdout);
#endif
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
}
int n, k, a[100000], b[100000], res;
int main()
{
// setup();
cin >> n >> k;
for (int i = 0; i < n; ++i)
{
cin >> a[i];
}
sort(a, a + n);
res = a[n - 1] - a[0] + 1;
for (int i = 0; i < n - 1; ++i)
{
b[i] = a[i + 1] - a[i] - 1;
}
sort(b, b + n - 1, greater<int>());
for (int i = 0; i < k - 1; ++i)
{
res -= b[i];
}
cout << res;
return 0;
}
