#include <bits/stdc++.h>
#define F first
#define S second
#define LL long long
#define rep(i, x) for(auto &i : (x))
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define left(x) ((x)<<1)
#define right(x) ((x)>>1)
#define LSOne(x) (x & -(x))
using namespace std;
using T = pair<pair<int, int>, int>;
const int SZ = 2e5 + 1;
const LL MOD = 1e9 + 7;
const LL INF = 1e18 + 1;
LL bp (LL b, LL e, LL m = MOD) {
if ( e == 0 ) return 1;
LL T = bp(b, e / 2);
T *= T; T %= m;
if ( e & 1 ) T *= b;
return T %= m;
}
LL nv_i (LL a) { return bp(a, MOD - 2); };
LL gcd (LL a, LL b) { return (b == 0 ? a : gcd(b, a % b)); }
LL lcm(LL a, LL b) { return (a * (b / gcd(a, b))); }
LL ceil (LL a, LL b) { return ((a + b - 1) / b); }
void solve() {
int n, k;
cin >> n >> k;
vector<int> V(n);
rep(i, V) cin >> i;
priority_queue<int> PQ;
for(int i = 1; i < n; i ++) {
PQ.push(V[i] - V[i - 1]);
}
LL cnt = n;
k --;
while(!PQ.empty() && k--)
PQ.pop();
while(!PQ.empty()) {
cnt += PQ.top() - 1;
PQ.pop();
}
cout << cnt;
}
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
solve();
return 0;
}
