Euler 5.2 modified

using namespace std;

#include <iostream>

double f(double x,double y){ // ôóíêöèÿ ïåðâîé ïðîèçâîäíîé
    return 5*x*x + 6*x*x;
}

int main(){
    double x,y,h;// x0, y0, øàã ñîîòâåòñòâåííî
    int n; // êîëè÷åñòâî èòòåðàöèé
    cout<<"x0=";
    cin>>x;
    cout<<"y0=";
    cin>>y;
    cout<<"h=";
    cin>>h;
    cout<<"n=";
    cin>>n;
    double yi=y;
    double xi=x;
    for (int i = 0;i<n;i++){
        yi+= h*f(x,y);
        xi+= h;
        y+=0.5*h*(f(x,y)+f(xi,yi));
        x+=h;
    }
    cout<<"x"<<n<<"="<<x<<endl;
    cout<<"y"<<n<<"="<<y<<endl;
    cout<<"f="<<f(x,y);
    return 0;
}