const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;
void async function () {
// Write your code here
while(line = await readline()){
const nums=line.split(' ').map(Number);
console.log(s(nums[0],nums[1], nums[2], nums[3], nums[4]))
function s(r, x, y, x1, y1){
let d1 = (x1 - x)**2 + (y1-y)**2;
var s1 = 0;
d = Math.sqrt(d1);
if( d%(2*r)===0){
s1 = Math.round(d/(2*r));
}else{
s1 = Math.round(d/(2*r))+1;
}
return s1;
}
}
}()