VK Cup 2017 - Round 2 A. Voltage Keepsake

#include <iostream> 
#include <stdio.h> 
#include <string.h> 
#include <stack> 
#include <queue> 
#include <map> 
#include <set> 
#include <vector> 
#include <math.h> 
#include <bitset> 
#include <algorithm> 

using namespace std;

#define X first
#define Y second
#define eps 1e-6
#define gcd __gcd
#define pb push_back
#define PI acos(-1.0)
#define lowbit(x) (x)&(-x)
#define bug printf("!!!!!\n");
#define mem(x,y) memset(x,y,sizeof(x))

typedef long long LL;
typedef long double LD;
typedef pair<int,int> pii;
typedef unsigned long long uLL;

const int N = 1e5+2;
const int INF  = 1<<30;
const int mod  = 1e9+7;

#define int long long 
int n,p,x[N],y[N];

inline bool check(double X){
    
  double nd=0;
  for(int i=1;i<=n;i++){
    
    if(y[i]*1.0/x[i]>=X) continue;
    nd+=(x[i]*X-y[i])/p;
  }
  if(X-nd>=eps) return 1;
  else return 0;
}
void solve(){
    
    scanf("%lld%lld",&n,&p);
    int sum=0;
    for(int i=1;i<=n;i++) scanf("%lld%lld",&x[i],&y[i]),sum+=x[i];
    if(p-sum>=0){
    
      cout<<-1<<endl;
      return ;
    }
    double l=0,r=1e10;
    while(r-l>eps){
    
      double mid=(l+r)/2.0;
      if(check(mid)){
    
        l=mid;
      }else r=mid-eps;
    } 
    double R=1e10;
    if(fabs(l-R)<=eps){
    
      cout<<-1<<endl;
    }else printf("%0.4lf\n", l);
    
    return;
}

int32_t main()
{
    
// freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
// ios::sync_with_stdio(false);
    int t = 1;
    //scanf("%d",&t);
    while(t--){
    
    // printf("Case %d: ",cas++);
        solve();
    }
    return 0;
}