#include <bits/stdc++.h>
#define ll long long
#define ff first
#define ss second
#define all(x) x.begin(), x.end()
#define pb push_back
#define ertunt return
#define vodka void
using namespace std;
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
ll n,k;
cin >> n >> k;
ll a[n];
for(ll i = 0; i < n; i++)cin >> a[i];
ll b[n-1];
ll ans = 0;
for(ll i = 0; i < n-1; i++){
b[i] = a[i+1] - a[i];
ans+=b[i];
}
sort(b,b+n-1);
reverse(b,b+n-1);
ans++;
k--;
ll j = 0;
while(k--){
ans-=b[j];
ans++;
j++;
}
cout << ans;
}
