http://www.51nod.com/Challenge/Problem.html#problemId=1257

#include
     
      #define fi first#define se second#define INF 0x3f3f3f3f#define LNF 0x3f3f3f3f3f3f3f3f#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0)#define pqueue priority_queue#define NEW(a,b) memset(a,b,sizeof(a))const double pi=4.0*atan(1.0);const double e=exp(1.0);const double eps=1e-10;const int maxn=4e5+8;typedef long long LL;typedef unsigned long long ULL;const LL mod=1e9+7;const ULL base=1e7+7;const int maxp=26+5;using namespace std;int w[maxn],p[maxn];pair
      
        d[maxn];int main(){    int n,k;    scanf("%d%d",&n,&k);    for(int i=1;i<=n;i++){        scanf("%d%d",&w[i],&p[i]);    }    double l=0.0,r=50001.0;    double mid;    double sz;    LL fz,fm;    while(l+eps<=r){        mid=(l+r)/2.0;        sz=0.0;        for(int i=1;i<=n;i++){            d[i].fi=(double)p[i]-mid*w[i];            d[i].se=i;        }        sort(d+1,d+1+n);        for(int i=n;i>=n-k+1;i--){            sz+=d[i].fi;        }        if(sz>=eps){            fm=0;            fz=0;            for(int i=n;i>=n-k+1;i--){                fm+=p[d[i].se];                fz+=w[d[i].se];            }            l=mid;        }        else{            r=mid;        }    }    LL g=__gcd(fm,fz);    fm/=g;    fz/=g;    cout<
       
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