/*
* @Author: hungeazy
* @Date: 2024-07-21 23:24:34
* @Last Modified by: hungeazy
* @Last Modified time: 2024-07-21 23:26:19
*/
#include <bits/stdc++.h>
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")
using namespace std;
#define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define int long long
#define ull unsigned long long
#define sz(x) x.size()
#define sqr(x) (1LL * (x) * (x))
#define all(x) x.begin(), x.end()
#define fill(f,x) memset(f,x,sizeof(f))
#define FOR(i,l,r) for(int i=l;i<=r;i++)
#define FOD(i,r,l) for(int i=r;i>=l;i--)
#define ii pair<int,int>
#define iii pair<int,ii>
#define di pair<ii,ii>
#define vi vector<int>
#define vii vector<ii>
#define mii map<int,int>
#define fi first
#define se second
#define pb push_back
#define MOD 1000000007
#define __lcm(a,b) (1ll * ((a) / __gcd((a), (b))) * (b))
#define YES cout << "YES\n"
#define NO cout << "NO\n"
#define MASK(i) (1LL << (i))
#define c_bit(i) __builtin_popcountll(i)
#define BIT(x,i) ((x) & MASK(i))
#define SET_ON(x,i) ((x) | MASK(i))
#define SET_OFF(x,i) ((x) & ~MASK(i))
#define oo 1e18
#define name ""
#define endl '\n'
#define time() cerr << endl << "-------------Time:" << 1000.0 * clock() / CLOCKS_PER_SEC << "ms.";
template<typename T> bool maximize(T &res, const T &val) { if (res < val){ res = val; return true; }; return false; }
template<typename T> bool minimize(T &res, const T &val) { if (res > val){ res = val; return true; }; return false; }
namespace hungeazy {
int fact5(int x)
{
int ans = 0;
while (x % 5 == 0) {x /= 5; ans++;}
return ans;
}
void solve(void)
{
int n;
cin >> n;
int t = 0, ans = 0;
while (t < n) {ans++; t += 1 + fact5(ans);}
cout << 5*ans;
}
}
signed main()
{
fast;
if (fopen(name".inp","r"))
{
freopen(name".inp","r",stdin);
freopen(name".out","w",stdout);
}
hungeazy::solve();
time();
return 0;
}
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//░▓█▒░██▓▒▒█████▓ ▒██░ ▓██░░▒▓███▀▒
// ▒ ░░▒░▒░▒▓▒ ▒ ▒ ░ ▒░ ▒ ▒ ░▒ ▒
// ▒ ░▒░ ░░░▒░ ░ ░ ░ ░░ ░ ▒░ ░ ░
// ░ ░░ ░ ░░░ ░ ░ ░ ░ ░ ░ ░ ░
// ░ ░ ░ ░ ░ ░#include <iostream>
using namespace std;
int main() {
// your code goes here
return 0;
}
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