#include "bits/stdc++.h"
using namespace std;
#ifdef N_N_C
#include "debug.h"
#else
#define cebug(...) "Arya"
#endif
#define int long long
const int N=1e5+5;
const int mod=1e9+7;
int n,k,a[N],d[N];
void sol(){
cin>>n>>k;
for(int i=1; i<=n; i++) cin>>a[i];
int ans=k+a[n]-a[1];
for(int i=1; i<n; i++) d[i]=a[i+1]-a[i];
int r=k-1;
sort(d+1,d+n,greater<int>());
for(int i=1; i<=r; i++) ans-=d[i];
cout<<ans;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
// freopen(".inp", "r", stdin);
// freopen(".out", "w", stdout);
int tt=1;
//cin>>tt;
while(tt--){
sol();
}
cerr << "\nTime elapsed: " << 1000.0 * clock() / CLOCKS_PER_SEC << " ms.\n";
return 0;
}
