/*
_.-- ,.--.
.' .' /
@ |'..--------._
/ \._/ '.
/ .-.- \
( / \ \
\\ '. | #
\\ \ -. /
:\ | )._____.' \
" | / \ | \ )
| |./' :__ \.-'
'--'
*/
#include<bits/stdc++.h>
#define ll long long
#define llll pair<int,int>
#define ii pair<int,int>
#define fi first
#define se second
#define FOR(i,l,r) for(int i=l;i<=r;i++)
#define FOD(i,r,l) for(int i=r;i>=l;i--)
#define ull unsigned long long
#define iii pair<int,ii>
#define iv pair<pii,ii>
#define db double
#define ld long double
#define pb push_back
using namespace std;
const int dx[] = {1, -1, 0, 0};
const int dy[] = {0, 0, -1, 1};
const int dxx[] = {1, 1, -1, -1, 2, 2, -2, -2};
const int dyy[] = {2, -2, 2, -2, 1, -1, 1, -1};
const ll INF=1e18;
const int N=1e5+5;
int a[N],b[N],n,k;ll ans;
void solve()
{
cin >> n >> k;
for(int i=1;i<=n;i++)
{
cin >> a[i];
}
for(int i=1;i<n;i++)
{
b[i]=a[i+1]-a[i];
}
sort(b+1,b+n);
for(int i=1;i<=n-k;i++)
{
ans+=b[i];
}
cout << ans+k;
}
int main()
{
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
// freopen("tdk.inp","r",stdin);
// freopen("tdk.out","w",stdout);
int t=1;
//cin >> t;
while(t--)
{
solve();
}
return 0;
}
