#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define int ll
#define ld long double
#define pii pair<int, int>
#define f first
#define s second
#define boost() cin.tie(0), cin.sync_with_stdio(0)
const int MN = 2005;
int n, m, dp[MN][MN];
pii a[MN];
void solve(int j, int l, int r, int p1, int p2) {
if (l > r) return;
int mid = (l + r) >> 1, opt = 0;
for (int p = p1; p <= min(p2, mid - 1); p++) {
if (dp[mid][j] < dp[p][j - 1] + a[mid].s - a[mid].f + a[p].f) {
dp[mid][j] = dp[p][j - 1] + a[mid].s - a[mid].f + a[p].f;
opt = p;
}
}
solve(j, l, mid - 1, p1, opt), solve(j, mid + 1, r, opt, p2);
}
int32_t main() {
boost();
cin >> n >> m;
for (int i = 1; i <= n; i++) cin >> a[i].s >> a[i].f, a[i].f *= 2;
sort(a + 1, a + n + 1);
int ans = -0x3f3f3f3f;
memset(dp, -0x3f, sizeof(dp));
for (int i = 1; i <= n; i++) dp[i][1] = a[i].s;
for (int j = 2; j <= m; j++) solve(j, 1, n, 1, n);
for (int i = 1; i <= n; i++) ans = max(ans, dp[i][m]);
printf("%lld\n", ans);
return 0;
}
