#include <bits/stdc++.h>
#define ll long long
#define dl double
#define str string
#define tst to_string
#define pb push_back
#define pf push_front
#define eb emplace_back
#define u_b upper_bound
#define l_b lower_bound
#define ff first
#define ss second
#define INF 1000000001
#define mxn 100001
#define mod 998244353
#define come_on ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
using namespace std;
struct modint {
int x;
modint(ll v = 0) { x = (v % mod + mod) % mod; }
modint operator+(const modint &o) const { return modint(x + o.x); }
modint operator-(const modint &o) const { return modint(x - o.x); }
modint operator*(const modint &o) const { return modint(1LL * x * o.x % mod); }
};
modint modpow(modint a, ll e)
{
modint res=1;
while(e)
{
if(e&1) res=res*a;
a=a*a;
e>>=1;
}
return res;
}
modint inv(modint a){ return modpow(a, mod - 2);}
modint operator/(const modint &a, const modint &b) {
return a*inv(b);
}
ostream &operator<<(ostream &os, const modint &m) {
return os << m.x;
}
void solve()
{
int n,k;
cin>>n>>k;
vector<ll>t(n);
for(int i=0;i<n;i++)
{
cin>>t[i];
}
ll total=(t[n-1]+1)-t[0];
vector<ll>v;
for(int i=0;i<n-1;i++)
{
ll gap=t[i+1]-(t[i]+1);
if(gap>0)
{
v.pb(gap);
}
}
sort(v.rbegin(),v.rend());
for(int i=0;i<k-1 && i<v.size();i++)
{
total-=v[i];
}
cout<<total<<'\n';
}
int main()
{
int T=1;
//cin>>T;
while(T--)
{
solve();
}
}
