$apiad$

$Code$

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=a;i<n;i++)
#define per(i,a,n) for (int i=n-1;i>=a;i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef basic_string<int> BI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
mt19937_64 mrand(random_device{}()); 
const ll mod=1000000007;
//int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

const int N=201000;
int n,k;
PII p[N];
ll dp[N][20];
int main() {
	scanf("%d%d",&n,&k);
	rep(i,0,n) scanf("%d%d",&p[i].fi,&p[i].se);
	sort(p,p+n,[&](PII a,PII b) {
		return a.se*b.fi>a.fi*b.se;
	});
	dp[0][0]=1;
	rep(i,0,n) rep(j,0,k+1) if (dp[i][j]!=0) {
		dp[i+1][j]=max(dp[i+1][j],dp[i][j]);
		if (j+1<=k) dp[i+1][j+1]=max(dp[i+1][j+1],dp[i][j]*p[i].fi+p[i].se);
	}
	printf("%lld\n",dp[n][k]);
}