#include <bits/stdc++.h>
using namespace std;
#define pf(a) printf("%.9f", a)
#define SZ size()
#define ll long long
#define pb push_back
#define BBC ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
void W2dNHK() {
ll n,k;
cin>>n>>k;
ll a[n+2];
ll i;
ll dih=0;
ll m=1e18,x=0;
ll z[n+11];
for(i=1 ; i<=n ; i++ ){
cin>>a[i];
m=min(m,a[i]);
x=max(n,a[i]);
}
dih=x-m+1;
ll g=0;
for(i=1 ; i<n ; i++ ){
z[i]=a[i+1]-a[i]-1;
}
sort(z+1,z+n);
for(i=n-1 ; i>=1 ;i--){
if(g==k - 1){
break;
}
dih-=z[i];
g++;
}
cout<<dih;
}
int main() {
BBC
ll tc = 1;
//cin >> tc;
while (tc--) {
W2dNHK();
}
}
