Language: C++

#include "bits/stdc++.h"
using namespace std;
#define Would
#define you
#define all(n)  n.begin(),n.end()
#define rall(n) n.rbegin(),n.rend()
typedef long long ll;
const ll INF = 2147483647;
const ll MOD = 1e9 + 7;
const double EPS = 1e-10;
const double pi = acos(-1);//3.1415926535897932384626433832795028...
const ll SIZE = 2000005;
int dx[] = { 1,0,-1,0 }, dy[] = { 0,1,0,-1 }, alp[30];
ll fac[SIZE], finv[SIZE], inv[SIZE];
vector<ll>dij;
struct edge { ll to, cost; };
vector<vector<edge> >G;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

ll mod_pow(ll a, ll b) {
	ll res = 1, mul = a;
	for (int i = 0; i < 31; ++i) {
		if (b >> i & 1) {
			res *= mul;
			res %= MOD;
		}
		mul = (mul * mul) % MOD;
	}
	return res;
}

void addedge(int from, int to, int cost) {
	G[from].push_back({ to,cost });
	G[to].push_back({ from,cost });
}

template<typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }

template<typename T, typename... Ts>
auto make_v(size_t a, Ts... ts) {
	return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

template<typename T, typename V>
typename enable_if<is_class<T>::value == 0>::type
fill_v(T & t, const V & v) { t = v; }

template<typename T, typename V>
typename enable_if<is_class<T>::value != 0>::type
fill_v(T & t, const V & v) {
	for (auto& e : t) fill_v(e, v);
}

template<typename T>
void outp(vector<T>v) {
	for (int i = 0; i < v.size(); ++i) {
		cout << v[i];
		if (i != v.size() - 1) { cout << " "; }
	}
}

double add(double a, double b) {
	if (abs(a + b) < EPS * (abs(a) + abs(b))) { return 0; }
	return a + b;
}

double len(int a, int b, int c, int d) {
	return (double)sqrt((a - c) * (a - c) + (b - d) * (b - d));
}

long long  gcd(long long  a, long long  b) {
	if (b == 0) return a;
	return gcd(b, a % b);
}

long long lcm(long long a, long long b) {
	long long  g = gcd(a, b);
	return a / g * b;
}

ll n, ans;
int main() 
	cin >> n;
	//odd
	if (n % 2 == 1) { cout << 0 << endl; return 0; }
	//even
	n /= 2;
	for (long long int i = 5; n / i >= 1; i *= 5) { ans += n / i; }
	cout << ans << endl;

}

Compiler output:
a.cc:85:9: error: expected initializer before 'cin'
   85 |         cin >> n;
      |         ^~~
a.cc:87:9: error: expected unqualified-id before 'if'
   87 |         if (n % 2 == 1) { cout << 0 << endl; return 0; }
      |         ^~
a.cc:89:9: error: 'n' does not name a type
   89 |         n /= 2;
      |         ^
a.cc:90:9: error: expected unqualified-id before 'for'
   90 |         for (long long int i = 5; n / i >= 1; i *= 5) { ans += n / i; }
      |         ^~~
a.cc:90:35: error: 'n' does not name a type
   90 |         for (long long int i = 5; n / i >= 1; i *= 5) { ans += n / i; }
      |                                   ^
a.cc:90:47: error: 'i' does not name a type
   90 |         for (long long int i = 5; n / i >= 1; i *= 5) { ans += n / i; }
      |                                               ^
a.cc:91:9: error: 'cout' does not name a type
   91 |         cout << ans << endl;
      |         ^~~~
a.cc:93:1: error: expected declaration before '}' token
   93 | }
      | ^