#include <bits/stdc++.h>
using namespace std;
#pragma GCC target("avx2")
#pragma GCC optimize("Ofast")
//#pragma comment(linker, "/stack:200000000")
#pragma GCC target( "sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native" )
#pragma GCC optimize("unroll-loops")
/*
#pragma GCC optimize("profile-values,profile-reorder-functions,tracer")
#pragma GCC optimize("vpt")
#pragma GCC optimize("rename-registers")
#pragma GCC optimize("move-loop-invariants")
#pragma GCC optimize("unswitch-loops")
#pragma GCC optimize("function-sections")
#pragma GCC optimize("data-sections")
#pragma GCC optimize("branch-target-load-optimize")
#pragma GCC optimize("branch-target-load-optimize2")
#pragma GCC optimize("btr-bb-exclusive")
#pragma GCC optimize("inline")
#pragma GCC optimize("-fgcse")
#pragma GCC optimize("-fgcse-lm")
#pragma GCC optimize("-fipa-sra")
#pragma GCC optimize("-ftree-pre")
#pragma GCC optimize("-ftree-vrp")
#pragma GCC optimize("-fpeephole2")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-fsched-spec")
#pragma GCC optimize("-falign-jumps")
#pragma GCC optimize("-falign-loops")
#pragma GCC optimize("-falign-labels")
#pragma GCC optimize("-fdevirtualize")
#pragma GCC optimize("-fcaller-saves")
#pragma GCC optimize("-fcrossjumping")
#pragma GCC optimize("-fthread-jumps")
#pragma GCC optimize("-freorder-blocks")
#pragma GCC optimize("-fschedule-insns")
#pragma GCC optimize("inline-functions")
#pragma GCC optimize("-ftree-tail-merge")
#pragma GCC optimize("-fschedule-insns2")
#pragma GCC optimize("-fstrict-aliasing")
#pragma GCC optimize("-falign-functions")
#pragma GCC optimize("-fcse-follow-jumps")
#pragma GCC optimize("-fsched-interblock")
#pragma GCC optimize("-fpartial-inlining")
#pragma GCC optimize("no-stack-protector")
#pragma GCC optimize("-freorder-functions")
#pragma GCC optimize("-findirect-inlining")
#pragma GCC optimize("-fhoist-adjacent-loads")
#pragma GCC optimize("-frerun-cse-after-loop")
#pragma GCC optimize("inline-small-functions")
#pragma GCC optimize("-finline-small-functions")
#pragma GCC optimize("-ftree-switch-conversion")
#pragma GCC optimize("-foptimize-sibling-calls")
#pragma GCC optimize("-fexpensive-optimizations")
#pragma GCC optimize("inline-functions-called-once")
#pragma GCC optimize("-fdelete-null-pointer-checks")
*/
#define ll long long
#define all(x) x.begin(),x.end()
#define sz(x) (int) x.size()
#define f first
#define s second
#define ld long double
#define yes cout << "YES" << endl
#define no cout << "NO" << endl
#define pb push_back
#define dauzhan gay
#define popcount __builtin_popcount
#define int long long
const long double Eps = 1e-12;
const int max1 = 1e9 + 100;
const int min1 = -1e9 *1.4;
const ll mod1 = 1000000007;
const ll mod2 = 2000000011;
const ll mod3 = 3000000017;
const ll mod = 998244353;
const int N = 2e5 + 100;
const int B = 1e6 + 1;
const ll INF = 1e18 + 100;
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ll binpow(ll x,ll y,ll md) {
if(y < 0) return 0;
if(y == 0) return 1;
if(y == 1) return x;
if(y % 2 == 0) {
ll now = binpow(x,y/2,md);
return (1ll*now*now) % md;
}
else {
ll now = binpow(x,y/2,md);
return (1ll*((1ll*now*now) % md)*x) % md;
}
}
/*
for(int i = 1;i <= n;i++) sp[0][i] = a[i];
for(int i = 1;i <= log2(n);i++) {
for(int l = 1;l <= n;l++) {
int r = l + (1 << i) - 1;
if(r > n) break;
int middle = l + (1 << (i - 1));
sp[i][l] = max(sp[i - 1][l],sp[i - 1][middle]);
}
}
int get(int l,int r) {
int g = log2(r - l + 1);
return max(sp[g][l],sp[g][r - (1 << g) + 1]);
}
*/
vector <int> reb[B];
bool was[B];
int mx[B],mn[B];
void dfs1(int v) {
mx[v] = v,mn[v] = v;
was[v] = true;
for(auto u:reb[v]) {
if(was[u]) continue;
dfs1(u);
mx[v] = max(mx[v],mx[u]);
mn[v] = min(mn[v],mn[u]);
}
}
bool was2[B];
void dfs2(int v) {
was2[v] = true;
for(auto u:reb[v]) {
}
}
signed main() {
ios_base::sync_with_stdio(NULL);
cin.tie(0);
cout.tie(0);
int n,k;
cin >> n >> k;
int t[n + 1];
for(int i = 1;i <= n;i++) cin >> t[i];
vector <int> v;
for(int i = 2;i <= n;i++) v.pb(t[i] - t[i - 1]);
sort(all(v));
int ans = n;
int ost = n - k;
for(int i = 0;i < ost;i++) {
ans+=v[i] - 1;
}
cout << ans << endl;
}
