#include<bits/stdc++.h> #define endl "\n" using namespace std ; typedef long long ll; typedef long double ld ; #define pb push_back #define pp pop_back const int N=1e6+9; const ll inf=1e18 ; const ll mod = 1e9+9 ; #define fast ios::sync_with_stdio(0);cin.tie(0);cout.tie(0); ll n ,a[N] , x, y,k,t[N]; vector<ll>vec; void solve(){ cin>>n>>k; for(int i=0;i<n;i++) cin>>t[i]; for(int i=0;i<(n-1);i++)vec.pb(t[i+1]-t[i]-1); sort(vec.begin(),vec.end()); ll ans=0; for(int i=0;i<(n-k);i++){ ans+=vec[i]; } cout<<n+ans; } int main(){ fast; ll t=1;//cin>>t; while(t--)solve(); return 0; }