#include<iostream.h>
#include<math.h>

void main()
{
	int n,i,j,p=1;
	double x1,f,x[100],y[100],s[100];
	
	cout<<"輸入數據組數：";
	cin>>n;
	for(i=0;i<n;i++)
    {   cout<<"x["<<i<<"]=";
		cin>>x[i];
		cout<<"y["<<i<<"]=";
		cin>>y[i];
	}
 

    while(p)
	{  
		cout<<"請輸入一個x的值："<<endl;
		cin>>x1;
		for(i=1;i<=n;i++) 
			s[i]=y[i]; 
        for(j=1;j<=n-1;j++) 
            for(i=n;i>=j+1;i--) 
				s[i]=(s[i]-s[i-1])/(x[i]-x[i-1]); 
        f=s[n]; 
        for(i=n-1;i>=1;i--) 
        f=f*(x1-x[i])+s[i]; 
        
		cout<<"當x的值為"<<x1<<"時的函數值為"<<f<<endl;

//-----------------------------------------------是否繼續？	
		cout<<"是否繼續計算別的函數值？是的話輸y"<<endl;
		char h;
		cin>>h;
		if((h=='y')||(h=='Y'))p=1;
		else p=0;

	}
}