/*
* imaN
* 49
*
*
**/
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define FF first
#define SS second
#define pb push_back
#define bp pop_back()
#define int long long
#define ld long double
#define pf push_front
#define Imansoska ios_base::sync_with_stdio(0);cin.tie(0); cout.tie(0);
#define endl cout << "\n"
/*int binpow (int a, int n, int m) {
if (n == 0)
return 1%m;
if (n % 2 == 1)
return binpow (a, n-1,m) * a%m;
else {
int b = binpow (a, n/2,m);
return b * b%m;
}
}
int lcm(int a, int b) {
return (a / __gcd(a, b)) * b;
}*/
const int N = (1e5+13);
const int maxn= 1e6+10;
const int MOD = 1e9 + 7;
const int INF = 1e18 + 7;
int z[N] , a[N];
signed main (/*Imansoska*/) {
Imansoska
// freopen("lepus.in","r",stdin);
// freopen("lepus.out","w",stdout);
int n,m;
cin >> n >> m;
int k=n-m;
for ( int i=1; i<=n; i++ ) {
cin >> z[i];
}
for ( int i=1; i<n; i++ ) {
a[i]=z[i+1]-z[i];
}
sort(a+1,a+n);
int s=m;
for (int i=1; i<=k; i++) {
s+=a[i];
}
cout<<s;
}
