Runge kutta method

#include<iostream.h>
float f(float a,float b)
{
    float c;
    c=0.5*(1+a)*b*b;
   return c;
}

void main()
{
    float x[20],y[20],h,del1,del2,del3,del4;
    int i,n;
    cout<<"\nEnter x(0),y(0),h,n=";
    cin>>x[0]>>y[0]>>h>>n;
    cout<<"\nx\ty\t\n";
    for(i=0;i<=n-1;i++)
    {
        x[i+1]=x[i]+h;
        del1=h*f(x[i],y[i]);
        del2=h*f(x[i]+h/2,y[i]+del1/2);
        del3=h*f(x[i]+h/2,y[i]+del2/2);
        del4=h*f(x[i]+h,y[i]+del3);
        y[i+1]=y[i]+(del1+2*del2+2*del3+del4)/6;
        cout<<endl<<x[i+1]<<"\t"<<y[i+1];
    }
}