#include <iostream>
#include <math.h>
using namespace std;
 
int main ()
{
    long long r, x0, y0, x1, y1;
    cin>>r>>x0>>y0>>x1>>y1;
    long long d = (x1-x0)*(x1-x0) + (y1-y0)*(y1-y0);
    double k=sqrt(d);
 
    if (x1==x0 && y1==y0)
    {
        cout<<"0";
    }
    else
    {
        if ((k/2)<=r)
            cout<<"1";
        else
        {
            long long dem=0;
            do
            {
                k=k-(double)(r*2);
                dem++;
           }
            while (k/2>r);    		
 
            cout<<dem+1;	
    	}	
    }
    return 0;
}

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