#include "bits/stdc++.h"
using namespace std;
#define int long long
#define fr first
#define sc second
#define eb emplace_back
const char nl = '\n';
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define dbg(x...) cerr << "LINE(" << __LINE__ << ") -> " <<"[" << #x << "] = ["; _print(x)
#else
#define dbg(x...)
#endif
void solve() {
int n, k; cin >> n >> k;
int t[n];
for(int &i : t) cin >> i;
int d[n - 1];
for(int i = 1; i < n; ++i) d[i - 1] = t[i] - t[i - 1] - 1;
sort(d, d + n - 1);
reverse(d, d + n - 1);
int res = t[n - 1] - t[0] + 1;
for(int i = 0; i < k - 1; ++i) res -= d[i];
cout << res;
}
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
int t = 1;
/* cin >> t; */
for(int i = 1; i <= t; ++i) {
/* cout << "Case #" << i << nl; */
solve();
/* cout << nl; */
}
}
