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;
        }
    }
}()