#include <iostream>  //四階龍格-庫塔方法
#include <math.h>
using namespace std;
#define MAX 100
float func(float x,float y);
int main()
{
    float a,s,b,h;
    float x[MAX],y[MAX],K[5];
    int n,N;
    cout<<"請分別輸入x[0],y[0],b,N并用空格隔開 "<<endl;
    cin>>a>>s>>b>>N;
    x[0]=a;
    y[0]=s;
    h=(b-a)/N;
    cout<<"結果為："<<endl;
    for (n=0;n<N;n++)
    {
        K[1]=h*func(x[n],y[n]);
        K[2]=h*func(x[n]+h/2,y[n]+K[1]/2);
        K[3]=h*func(x[n]+h/2,y[n]+K[2]/2);
        K[4]=h*func(x[n]+h,y[n]+K[3]);
        x[n+1]=a+(n+1)*h;
        y[n+1]=y[n]+(K[1]+2*K[2]+2*K[3]+K[4])/6;


        cout<<x[n+1]<<"       "<<y[n+1]<<endl;

    }
    return 0;
}

float func(float x,float y)
{
    float f=-20*(y-x*x)+2*x;
    return f;
}