#include<bits/stdc++.h>
// #include"virus.cpp"
#define IOS ios_base::sync_with_stdio(false),cin.tie(NULL),cout.tie()
#define ll long long
#define ull unsigned long long
#define pb push_back
// #define endl "\n"
#define int ll
#define F first
#define S second
#define pii pair<int,int>
#define db double
#define ld long double
#define short unsigned short
using namespace std;
const int inf = 1e9,MOD=1e9+7,N=2005,MN=1e9+7;
void solve() {
int n,k;
cin>>n>>k;
vector<int>v(n);
for(int i=0;i<n;i++){
cin>>v[i];
}
vector<int>g(n-1);
for(int i=1;i<n;i++){
g[i-1]=v[i]-v[i-1]-1;
}
sort(g.begin(),g.end());
int loh=n-k;
int ans=n;
int i=0;
while(loh--){
ans+=g[i];
i++;
}
cout<<ans<<endl;
}
signed main() {
IOS;
//freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
int UwU=1;
// cin>>UwU;
while (UwU--) {
solve();
}
}
