#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
typedef tree<
int,
null_type,
less_equal<int>,
rb_tree_tag,
tree_order_statistics_node_update> ordered_set;
typedef tree<
int,
null_type,
less<int>,
rb_tree_tag,
tree_order_statistics_node_update> ordered_multiset;
#define all(v) ((v).begin()), ((v).end())
#define sz(v) ((int)((v).size()))
#define pb push_back
typedef long long ll;
void solve(){
int n,k;
cin>>n>>k;
vector<int>v(n);
for(int i=0;i<n;i++){
cin>>v[i];
}
if(n==1){
cout<<1<<"\n";
return;
}
if(k==1){
cout<<v.back()-v[0]+1<<"\n";
return;
}
vector<pair<int,int>>d;
for(int i=0;i<n-1;i++){
d.pb({v[i+1]-v[i],-i});
}
sort(all(d));
reverse(all(d));
vector<int>idx;
for(int i=0;i<k-1;i++){
idx.pb(-d[i].second);
}
sort(all(idx));
ll res=0,s=v[0];
for(int i=0;i<idx.size();i++){
res+=v[idx[i]]-s+1;
s=v[idx[i]+1];
}
res+=v.back()-s+1;
cout<<res;
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
int t=1;
// cin>>t;
while(t--) solve();
}
