FizzBuzz http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=2441

aoj2441.cpp

#include <bits/stdc++.h>
using namespace std;
#define int long long   // <-----!!!!!!!!!!!!!!!!!!!

#define rep(i,n) for (int i=0;i<(n);i++)
#define rep2(i,a,b) for (int i=(a);i<(b);i++)
#define rrep(i,n) for (int i=(n)-1;i>=0;i--)
#define rrep2(i,a,b) for (int i=(a)-1;i>=b;i--)
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
#define printV(_v) for(auto _x:_v){cout<<_x<<" ";}cout<<endl
#define printVS(_vs) for(auto _x : _vs){cout << _x << endl;}
#define printVV(_vv) for(auto _v:_vv){for(auto _x:_v){cout<<_x<<" ";}cout<<endl;}
#define printP(_p) cout << _p.first << " " << _p.second << endl
#define printVP(_vp) for(auto _p : _vp) printP(_p);

typedef long long ll;
typedef pair<int, int> Pii;
typedef tuple<int, int, int> TUPLE;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<vector<int>> Graph;
const int inf = 1e9;
const int mod = 1e9 + 7;

// [1, x]に含まれる3でも5でも割り切れない整数の個数
int f(int x) {
    int n3 = x / 3;
    int n5 = x / 5;
    int n15 = x / 15;
    return x - n3 - n5 + n15;
}

// 数xまで書いたときの文字列の長さ
int calc(int x) {
    int ret = 0;
    ret += 4 * (x / 3 + x / 5);

    int a = 0;
    int b = 9;
    rep(i, 100) {
        bool finish = false;
        if (x <= b) {
            b = x;
            finish = true;
        }
        // [a, b]に含まれる3でも5でも割り切れない整数の個数
        int m = f(b) - f(a);
        ret += (i + 1) * m;
        if (finish) {
            return ret;
        }
        a = b + 1;
        b = 10 * a - 1;
    }
}

signed main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);

    int n;
    cin >> n;

    int l = 0, r = 1e18;
    while (r - l > 1) {
        int m = (l + r) / 2;
        (calc(m) < n ? l : r) = m;
    }

    string s;
    rep2(x, l + 1, l + 100) {
        if (x % 3 == 0) s += "Fizz";
        if (x % 5 == 0) s += "Buzz";
        if (x % 3 != 0 && x % 5 != 0) s += to_string(x);
    }
    cout << s.substr(n - calc(l) - 1, 20) << endl;
}