#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fi first
#define se second
constexpr ll MAXN=3e5+5,MAXV=1e5,MOD=1e9+7,INF=1e18;
ll n,m,i,j,p,k,ans,dem,st,en,a[MAXN],mark[MAXN];
vector<pair<ll,ll>> dist;
int main(){
ios::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
// freopen("test.inp","r",stdin);
// freopen("test.out","w",stdout);
cin>>n>>m;
m--;
dist.pb({0,1});
for(i=1;i<=n;i++){
cin>>a[i];
if(i>1)
dist.pb({a[i]-a[i-1],i});
}
sort(dist.begin(),dist.end(),greater<pair<ll,ll>>());
while(dist.size()>m){
auto k=dist[dist.size()-1];
ans+=k.fi;
if(!mark[k.se]&&!mark[k.se-1])
ans++;
else if(mark[k.se]&&mark[k.se-1])
ans--;
mark[k.se]=1,mark[k.se-1]=1;
dist.pop_back();
}
for(i=1;i<=n;i++)
if(!mark[i]) ans++;
cout<<ans;
}
