Как увеличить число проходов массива?

#include "pch.h"
#include <iostream>
#include <cmath>
using namespace std;
 
double F(double x, double y) {
    return 0.6 * sin(x) - 1.25*y*y + 1;
}
 
int main() {
    double a = 0; double b = 1; double p = 0.0041 ; double n = 20;
    double h = (b - a) / n;
    double *X = new double[n];
    double *Y1 = new double[n];
    double *Y = new double[n];
    X[0] = a; Y[0] = 0;
    for (int i = 1; i <= n; i++) {
        X[i] = a + i * h;
        Y1[i] = Y[i - 1] + h * F(X[i - 1], Y[i - 1]);
        Y[i] = Y[i - 1] + h * (F(X[i - 1], Y[i - 1]) + F(X[i], Y1[i])) / 2.0;
        cout << "Y[" << i << "]=" << Y[i] << endl;
    }
    return 0;
}

#include <iostream>
#include <cmath>
#include <fstream>
using namespace std;
 
double F(double x, double y) {
    return 0.6 * sin(x) - 1.25*y*y + 1;
}
 
int main() {
 
    double a = 0; double b = 1; double p = 0.0041 ;
    int n = 20;
    double h = (b - a) / n;
    double *X = new double[n];
    double *Y1 = new double[n];
    double *Y = new double[n];
    ofstream oFile("output.txt");
    if(!oFile){
        cout << "file not open!!!";
        return 1;
    }
    X[0] = a; Y[0] = 0;
    for (int i = 1; i <= n; i++) {
        X[i] = a + i * h;
        Y1[i] = Y[i - 1] + h * F(X[i - 1], Y[i - 1]);
        Y[i] = Y[i - 1] + h * (F(X[i - 1], Y[i - 1]) + F(X[i], Y1[i])) / 2.0;
        cout << "Y[" << i << "]=" << Y[i] << endl;
        oFile << "Y[" << i << "]=" << Y[i] << endl;
    }
    return 0;
}