/*
███╗ ███╗ █████╗ ██████╗ ███████╗ ██████╗ ██╗ ██╗ ███╗ ███╗ █████╗ ██████╗ ██████╗██╗ ██╗███████╗██╗ ██╗ ██╗ ██╗██╗██╗
████╗ ████║██╔══██╗██╔══██╗██╔════╝ ██╔══██╗╚██╗ ██╔╝██╗ ████╗ ████║██╔══██╗██╔══██╗██╔════╝██║ ██║██╔════╝██║ ██║ ██║ ██║██║██║
██╔████╔██║███████║██║ ██║█████╗ ██████╔╝ ╚████╔╝ ╚═╝ ██╔████╔██║███████║██████╔╝██║ ███████║█████╗ ██║ ██║ ███████║██║██║
██║╚██╔╝██║██╔══██║██║ ██║██╔══╝ ██╔══██╗ ╚██╔╝ ██╗ ██║╚██╔╝██║██╔══██║██╔══██╗██║ ██╔══██║██╔══╝ ██║ ██║ ██╔══██║██║██║
██║ ╚═╝ ██║██║ ██║██████╔╝███████╗ ██████╔╝ ██║ ╚═╝ ██║ ╚═╝ ██║██║ ██║██║ ██║╚██████╗██║ ██║███████╗███████╗███████╗█████╗██║ ██║██║██║
╚═╝ ╚═╝╚═╝ ╚═╝╚═════╝ ╚══════╝ ╚═════╝ ╚═╝ ╚═╝ ╚═╝╚═╝ ╚═╝╚═╝ ╚═╝ ╚═════╝╚═╝ ╚═╝╚══════╝╚══════╝╚══════╝╚════╝╚═╝ ╚═╝╚═╝╚═╝
*/
/*
ඞ
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⣠⣤⣤⣤⣤⣤⣤⣤⣤⣄⡀
⠀⠀⠀⠀⠀⠀⠀⠀⢀⣴⣿⡿⠛⠉⠉⠉⠉⠉⠉⠻⢿⣿⣷⡄
⠀⠀⠀⠀⠀⠀⠀⠀⣼⣿⠋⠀⠀⠀⠀⠀⠀⠀ ⢻⣿⣿⡄
⠀⠀⠀⠀⠀⠀⠀⣸⣿⡏⠀⠀⠀ ⣠⣾⣿⣿⣿⠿⠿⠿⢿⣿⣿⣄
⠀⠀⠀⠀⠀⠀⠀⣿⣿⠁⠀⠀ ⣿⣿⣯⠁⠀⠀⠀⠀⠀ ⠙⢿⣷⡄
⠀⠀⣀⣤⣴⣶⣶⣿⡟⠀⠀⠀ ⣿⣿⣿ ⣿⣷
⠀⢰⣿⡟⠋⠉⣹⣿⡇⠀⠀⠀ ⣿⣿⣿⣷⣦⣀⣀⣀⣀⣀⣀⣀⣿⣿
⢸⣿⡇ ⣿⣿⡇⠀⠀ ⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿
⣸⣿⡇ ⣿⣿⡇⠀⠀⠀⠀ ⠉⠉⠉⠉⠉⠉⠉⠉⠉⡿⢻⡇
⠀⣿⣿ ⣿⣿⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⢸⣿⡇
⠀⣿⣿⠀ ⣿⣿⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⢸⣿⡇
⠀⣿⣿⠀⠀ ⣿⣿⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⢸⣿⡇
⠀⢿⣿ ⠀⣿⣿⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⣿⡇
⠀⠸⣿⣦⡀⠀⣿⣿⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⣿⣿
⠀⠀⠛⢿⣿⣿⣿⣿⡇ ⠀⣠⣿⣿⣿⣿⣄ ⣿⣿
⠀⠀⠀⠀⠀⠀⠀⣿⣿⠀⠀⠀⠀⠀⣿⣿⡇⠀⣽⣿⡆ ⢸⣿⡇
⠀⠀⠀⠀⠀⠀⠀⣿⣿⠀⠀⠀⠀⠀⣿⣿⡇⠀⢹⣿⡆⠀⠀ ⣸⣿⠇
⠀⠀⠀⠀⠀⠀⠀⢿⣿⣦⣄⣀⣠⣴⣿⣿ ⠀⠈⠻⣿⣿⣿⣿⡿⠏
⠀⠀⠀⠀⠀⠀⠀⠈⠛⠻⠿⠿⠿⠿⠋⠁
*/
#include<bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define pll pair<ll, ll>
#define plll pair<pll, pll>
#define pdd pair<double, double>
#define pu push_back
#define po pop_back
#define fi first
#define se second
#define fifi fi.fi
#define fise fi.se
#define sefi se.fi
#define sese se.se
#define cekcek cout<<'c'<<'e'<<'k'<<endl
using namespace std;
ll N, M, A[100005], pos, ans;
bool udh;
pll B[100005];
map<ll, pll> p;
bool compare(pll x, pll y){
return x.se - x.fi < y.se - y.fi;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
cin >> N >> M;
for(ll i = 1; i <= N; i++){
cin >> A[i];
p[A[i]] = {A[i], A[i]};
if(i > 1) B[i - 1] = {A[i - 1], A[i]};
}
sort(B + 1, B + N, compare);
for(ll i = 1; i <= N - M; i++){
p[B[i].fi].se = B[i].se;
p[B[i].se].fi = B[i].fi;
}
// for(ll i = 1; i < N; i++){
// cout << B[i].fi << " " << B[i].se << endl;
// }
// for(ll i = 1; i <= N; i++){
// cout << p[A[i]].fi << " " << p[A[i]].se << endl;
// }
udh = true;
pos = -1;
for(ll i = 1; i <= N; i++){
if(pos == i){
udh = true;
continue;
}
if(!udh) continue;
pos = i;
while(p[A[pos]].se != A[pos]) pos++;
//cout << i << " " << pos << endl;
ans += A[pos] - A[i] + 1;
if(i < pos) udh = false;
}
cout << ans << endl;
}
