/*
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*/
//#include <bits/BaoMinhTranc++.h>
#include <bits/stdc++.h>
#define int int64_t
//#define ll int64_t
#define ld long double
#define ii pair<int,int>
#define iii pair<int,ii>
#define fi first
#define se second
#define ALL(x) x.begin(),x.end()
#define ALLr(x) x.rbegin(),x.rend()
#define upgrade ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
using namespace std;
const int Max=3e5;
const int N=3e5+3;
const int INF=1e18;
const int MOD=1e9+7;
const int MOD2=1e9+8;
const int base=26;
const int LOG=20;
template<class X,class Y>
bool minimize(X& x,const Y& y)
{
if(x>y){
x=y;
return 1;
}return 0;
}
template<class X,class Y>
bool maximize(X& x,const Y& y)
{
if(x<y){
x=y;
return 1;
}return 0;
}
int t[N];
int a[N];
int n,k;
void solve()
{
cin>>n>>k;
for(int i=1;i<=n;i++)cin>>t[i];
int s=t[n]-t[1]+1;
for(int i=1;i<n;i++)a[i]=t[i+1]-t[i]-1;
sort(a+1,a+n);
reverse(a+1,a+n);
for(int i=1;i<k;i++)s-=a[i];
cout<<s;
}
void prepare()
{
}
signed main()
{
upgrade
// freopen("NKSEX.INP","r",stdin);
// freopen("NKSEX.OUT","w",stdout);
prepare();
int test=1;
// cin>>test;
while(test--)solve();
return 0;
}
/*
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*/
