var arr = readline().split(" ").map(function(v) {return +v;});
var r = arr[0];
var x = arr[1];
var y = arr[2];
var xx = arr[3];
var yy = arr[4];

var r2 = r*r;
var d2 = (xx-x)*(xx-x)+(yy-y)*(yy-y);

var res = Math.sqrt(d2)/2/r;
var ans = res<1&&res>0?1:0;
ans += Math.ceil(res);

print(ans);
