#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
#define pb push_back
#define yes cout<<"YES"<<endl
#define no cout<<"NO"<<endl
void afterdot(int n){
cout<<setprecision(n)<<fixed;
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
int n,m;
cin>>n>>m;
int a[n+2];
for(int i=1;i<=n;i++){
cin>>a[i];
}
int b[n+2];
for(int i=1;i<n;i++){
b[i]=a[i+1]-a[i];
}
sort(b+1,b+n);
int ans=0;
for(int i=1;i<=n-m;i++){
ans+=b[i];
}
ans+=(m);
cout<<ans<<endl;
}
