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#include <bits/stdc++.h>
using namespace std;
#define int long long
#define resetIO(x) \
freopen(#x ".in", "r", stdin), freopen(#x ".out", "w", stdout)
#define debug(fmt, ...) \
fprintf(stderr, "[%s:%d] " fmt "\n", __FILE__, __LINE__, ##__VA_ARGS__)
template <class _Tp>
inline _Tp& read(_Tp& x) {
bool sign = false;
char ch = getchar();
long double tmp = 1;
for (; !isdigit(ch); ch = getchar())
sign |= (ch == '-');
for (x = 0; isdigit(ch); ch = getchar())
x = x * 10 + (ch ^ 48);
if (ch == '.')
for (ch = getchar(); isdigit(ch); ch = getchar())
tmp /= 10.0, x += tmp * (ch ^ 48);
return sign ? (x = -x) : x;
}
template <class _Tp>
inline void write(_Tp x) {
if (x < 0)
putchar('-'), x = -x;
if (x > 9)
write(x / 10);
putchar((x % 10) ^ 48);
}
template <const int MAXV, const int MAXE>
struct MCMF {
const int INF = 0x3f3f3f3f3f3f3f3f;
struct Edge {
int v, flow, cost;
} edge[MAXE * 2];
int tot = 1, head[MAXV], nxt[MAXE];
int flow, cost, cur[MAXV], dis[MAXV];
bool vis[MAXV];
void addedge(int u, int v, int flow, int cost) {
edge[++tot] = {v, flow, cost};
nxt[tot] = head[u], head[u] = tot;
edge[++tot] = {u, 0, -cost};
nxt[tot] = head[v], head[v] = tot;
}
bool spfa(int s, int t) {
fill(vis, vis + MAXV, 0);
fill(dis, dis + MAXV, -INF);
queue<int> que;
que.push(s);
dis[s] = 0;
vis[s] = 1;
while (!que.empty()) {
int u = que.front();
que.pop();
vis[u] = 0;
for (int i = head[u]; i; i = nxt[i]) {
int v = edge[i].v;
if (edge[i].flow && dis[v] < dis[u] + edge[i].cost) {
dis[v] = dis[u] + edge[i].cost;
if (!vis[v]) {
que.push(v);
vis[v] = 1;
}
}
}
}
return dis[t] != -INF;
}
int augment(int u, int t, int mx) {
if (u == t || mx == 0)
return mx;
vis[u] = 1;
int ret = 0;
for (int &i = cur[u]; i; i = nxt[i]) {
int v = edge[i].v;
if (vis[v] || dis[v] != dis[u] + edge[i].cost)
continue;
int tmp = augment(v, t, min(mx, edge[i].flow));
cost += tmp * edge[i].cost;
mx -= tmp, ret += tmp;
edge[i].flow -= tmp, edge[i ^ 1].flow += tmp;
if (mx == 0)
break;
}
vis[u] = 0;
return ret;
}
pair<int, int> mcmf(int s, int t) {
while (spfa(s, t)) {
copy(head, head + MAXV, cur);
flow += augment(s, t, INF);
}
return make_pair(flow, cost);
}
};
const int MAXN = 1e3 + 10;
const int MAXM = 1e4 + 10;
const int INF = 0x3f3f3f3f3f3f3f3f;
int n, k, m, a[MAXN], l[MAXN], r[MAXN], p[MAXN];
MCMF<MAXN, MAXM> network;
signed main() {
read(n), read(k);
for (int i = 1; i <= n; ++i) {
read(l[i]), read(r[i]);
p[++m] = l[i], p[++m] = r[i];
a[i] = r[i] - l[i];
}
p[++m] = -INF, p[++m] = INF;
sort(p + 1, p + m + 1);
m = unique(p + 1, p + m + 1) - p - 1;
for (int i = 1; i <= n; ++i) {
l[i] = lower_bound(p + 1, p + m + 1, l[i]) - p;
r[i] = lower_bound(p + 1, p + m + 1, r[i]) - p;
network.addedge(l[i], r[i], 1, a[i]);
}
for (int i = 1; i < m; ++i)
network.addedge(i, i + 1, k, 0);
write(network.mcmf(1, m).second), putchar('\n');
return 0;
}
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