Language: C++

boxbox#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i=0;i<n;i++)
#define all(cont) cont.begin(), cont.end()
#define unique(a)  sort(all(a)) , (a).erase(unique((a).begin(), (a).end()),(a).end())
#define rall(cont) cont.rbegin(), cont.rend()
#define sz(x) (int)(x).size()
#define fastio          ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define PB push_back
#define endl "\n"
#define f first
#define s second
#define mset(m,v) memset(m,v,sizeof(m))
#define mod 1000000007
const int N = 2e5 + 5, INF = 1E9 + 7;
#define PI acos(-1.0)
long double EPS = 1e-9;
typedef long long ll;
#define int long long
typedef long double ld;
typedef vector<int> vi;
typedef pair<int, int> pii;
typedef vector<pair<int, int>> vpii;
#define pqll_max priority_queue<ll> // max heap. push(),pop(),top(),size(),empty()
#define pqll_min priority_queue<ll,vector<ll>,greater<ll> >
#define lb(v,val)   lower_bound(v.begin(),v.end(),val) //first equal to or lower than [------------
#define ub(v,val)   upper_bound(v.begin(),v.end(),val) //first greater than ------------)
#define bs(v,x) binary_search(v.begin(),v.end(),x)
inline ll add(ll x, ll y) { x += y; if (x >= mod) x -= mod; return x; }
inline ll sub(int x, int y) { x -= y; if (x < 0) x += mod; return x; }
inline ll mul(ll x, ll y) { return (x%mod * 1ll * y%mod) % mod; }
inline ll pwr(ll a, ll b) { ll x = 1 % mod; while (b) { if (b & 1) x = mul(x, a); a = mul(a, a); b >>= 1; }return x % mod; }
inline ll inv(ll a) { return pwr(a, mod - 2) % mod; }
ll gcd(ll a, ll b) { if (!a)return b % mod; return gcd(b%a, a) % mod; }
#define debug(x) cout << #x << " = " << x << endl;
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void __f(const char* name, Arg1&& arg1) {
	cout << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args) {
	const char* comma = strchr(names + 1, ','); cout.write(names, comma - names) << " : " << arg1 << " | "; __f(comma + 1, args...);
}
#define in(container) for (auto &it : container) cin>>it;
#define out(container) for (auto it : container) cout << it << " "; cout << endl;
void solve() {
	string s;
	cin >> s;
	if (s[sz(s) - 1] != 's') {
		cout << s + 's' << endl;
	}
	else {
		cout << s+ "es" << endl;
	}
}
signed main()
{
	fastio;
	//cout<<fixed<<setprecision(15);
	//clock_t begin = clock();
	int tc;
	tc = 1;
	//cin >> tc;
	while (tc--) {
		solve();
	}
	//clock_t end = clock();double elapsed_secs = double(end - begin) / CLOCKS_PER_SEC;cerr << elapsed_secs;
}


//Error?
// clear lists for every test case
// print new line for each tc
// check for int or ll
// check if problem can be solved without any heavy DS like priority_queue or map



Compiler output:
a.cc:1:7: error: stray '#' in program
    1 | boxbox#include <bits/stdc++.h>
      |       ^
a.cc:1:1: error: 'boxbox' does not name a type
    1 | boxbox#include <bits/stdc++.h>
      | ^~~~~~
a.cc:21:9: error: 'vector' does not name a type
   21 | typedef vector<int> vi;
      |         ^~~~~~
a.cc:22:9: error: 'pair' does not name a type
   22 | typedef pair<int, int> pii;
      |         ^~~~
a.cc:23:9: error: 'vector' does not name a type
   23 | typedef vector<pair<int, int>> vpii;
      |         ^~~~~~
a.cc: In function 'void __f(const char*, Arg1&&)':
a.cc:39:9: error: 'cout' was not declared in this scope; did you mean 'out'?
   39 |         cout << name << " : " << arg1 << endl;
      |         ^~~~
      |         out
a.cc: In function 'void __f(const char*, Arg1&&, Args&& ...)':
a.cc:43:29: error: there are no arguments to 'strchr' that depend on a template parameter, so a declaration of 'strchr' must be available [-fpermissive]
   43 |         const char* comma = strchr(names + 1, ','); cout.write(names, comma - names) << " : " << arg1 << " | "; __f(comma + 1, args...);
      |                             ^~~~~~
a.cc:43:29: note: (if you use '-fpermissive', G++ will accept your code, but allowing the use of an undeclared name is deprecated)
a.cc:43:53: error: 'cout' was not declared in this scope; did you mean 'out'?
   43 |         const char* comma = strchr(names + 1, ','); cout.write(names, comma - names) << " : " << arg1 << " | "; __f(comma + 1, args...);
      |                                                     ^~~~
      |                                                     out
a.cc: In function 'void solve()':
a.cc:48:9: error: 'string' was not declared in this scope
   48 |         string s;
      |         ^~~~~~
a.cc:49:9: error: 'cin' was not declared in this scope; did you mean 'in'?
   49 |         cin >> s;
      |         ^~~
      |         in
a.cc:12:11: error: 'second' was not declared in this scope
   12 | #define s second
      |           ^~~~~~
a.cc:49:16: note: in expansion of macro 's'
   49 |         cin >> s;
      |                ^
a.cc:51:17: error: 'cout' was not declared in this scope; did you mean 'out'?
   51 |                 cout << s + 's' << endl;
      |                 ^~~~
      |                 out
a.cc:54:17: error: 'cout' was not declared in this scope; did you mean 'out'?
   54 |                 cout << s+ "es" << endl;
      |                 ^~~~
      |                 out
a.cc: In function 'int main()':
a.cc:8:25: error: 'ios_base' has not been declared
    8 | #define fastio          ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
      |                         ^~~~~~~~
a.cc:59:9: note: in expansion of macro 'fastio'
   59 |         fastio;
      |         ^~~~~~
a.cc:8:54: error: 'cin' was not declared in this scope; did you mean 'in'?
    8 | #define fastio          ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
      |                                                      ^~~
a.cc:59:9: note: in expansion of macro 'fastio'
   59 |         fastio;
      |         ^~~~~~
a.cc:8:65: error: 'cout' was not declared in this scope; did you mean 'out'?
    8 | #define fastio          ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
      |                                                                 ^~~~
a.cc:59:9: note: in expansion of macro 'fastio'
   59 |         fastio;
      |         ^~~~~~