#define N 100
#include"iostream.h"
 float Y[N],X[N];
 int n,k=1;
 float x;
 float sum,s;
float f(int i,int j)
{
  float sum1=0;
  if(j-i==1) sum1=(Y[j]-Y[i])/(X[j]-X[i]);
  else sum1=(f(i+1,j)-f(i,j-1))/(X[j]-X[i]);
  if(i==0&&j==k)
  {
    sum+=sum1*s;
 s*=(x-X[k]);
 k++;
  }
  return sum1;
}

 void main()
{
  cout<<"輸入你想進行的X次多項試計算:";
  cin>>n;
  for(int i=0;i<=n;i++)
  {
    cout<<"輸入第"<<i+1<<"個點的坐標:";
 cin>>X[i]>>Y[i];
  }
  sum=Y[0];
  cout<<"輸入你想進行計算的x值:";
  cin>>x;
  s=(x-X[0]);
  f(0,n);
  cout<<sum;
}