#include <bits/stdc++.h>
using namespace std;
inline int in() {
int result = 0;
char ch = getchar_unlocked();
while(true) {
if(ch >= '0' && ch <= '9')
break;
ch = getchar_unlocked();
}
result = ch-'0';
while(true) {
ch = getchar_unlocked();
if (ch < '0' || ch > '9')
break;
result = result*10 + (ch - '0');
}
return result;
}
inline void out(int x) {
int rev=x, c=0;
while(!(rev%10)) {
++c;
rev/=10;
}
rev=0;
while(x) {
rev=rev*10+x%10;
x/=10;
}
while(rev) {
putchar_unlocked(rev%10+'0');
rev/=10;
}
while(c--)
putchar_unlocked('0');
}
const int mxN=1e5;
int n, k, t1, t2, ans, d[mxN-1];
int main() {
n=in(), k=in();
for(int i=0; i<n; ++i) {
t2=in();
if(i)
d[i-1]=t2-t1-1;
t1=t2;
}
ans=n;
sort(d, d+n-1);
for(int i=0; i<n-k; ++i)
ans+=d[i];
out(ans);
}
