#include<iostream> #include<vector> #include<algorithm> #define ll long long using namespace std; int main(){ int n,k; cin>>n>>k; vector<ll> t(n); for(int i=0;i<n;i++) cin>>t[i]; vector<ll> inter; for(int i=0;i<n-1;i++) inter.push_back(t[i+1]-t[i]-1); sort(inter.begin(),inter.end()); reverse(inter.begin(),inter.end()); ll ans=t[n-1]-t[0]+1; for(int i=0;i<k-1;i++) ans-=inter[i]; cout<<ans<<"\n"; }