1618-trailing-zeros.cpp

#include <bits/stdc++.h>
using namespace std;

#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define ll long long
#define vi vector<int>
#define vl vector<ll>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pb push_back
#define mp make_pair
#define fi first
#define se second

const int MOD = 1e9 + 7;
const int INF = 1e9;
const ll LLINF = 1e18;

void solve() {
    ll n;
    cin >> n;

    ll count = 0;
    ll divisor = 5;

    while (n / divisor > 0) {
        count += n / divisor;
        divisor *= 5;
    }

    cout << count << "\n";
}

int main() {
    fastio

    int tc = 1; // Number of test cases
    // cin >> tc;

    while (tc--) {
        solve();
    }

    return 0;
}