#define NDEBUG
#ifdef NDEBUG
#define dbg(TXTMSG) if constexpr (false) cerr << "lol"
#define dbgv(VARN) ((void)0)
#define dbgfor(COND) if constexpr (false) for (COND)
#else
#define _GLIBCXX_DEBUG 1
#define _GLIBCXX_DEBUG_PEDANTIC 1
#pragma GCC optimize("trapv")
#define dbg(TXTMSG) cerr << "\n" << TXTMSG
#define dbgv(VARN) cerr << "\n" << #VARN << " = "<< VARN << ", line: " << __LINE__ << "\n"
#define dbgfor(COND) for (COND)
#endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll,ll>;
#define e0 first
#define e1 second
constexpr ll INFTY = 2e18;
int main() {
cin.tie(nullptr);
ios_base::sync_with_stdio(false);
ll N,K;
cin >> N >> K;
vector<ll> T(N);
for (ll i = 0; i < N; ++i)
{
cin >> T[i];
}
vector<ll> segs(N-1);
for (ll i = 0; i < N-1; ++i)
{
segs[i] = T[i+1]-T[i] -1;
}
sort(segs.begin(),segs.end());
K--;
ll savings=0;
while (!segs.empty() && K>0) {
savings += *segs.crbegin();
segs.pop_back();
K--;
}
dbgv(savings);
cout << T[N-1]-T[0]+1 - savings;
}
