Language: C++

#include<bits/stdc++.h>
#include<cmath>
#pragma GCC optimize("Ofast")
using namespace std;
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
typedef long long ll;
const ll MOD = 1000000007;
#define rep(i,n) for(ll i=0, i##_len=(n); i<i##_len; ++i)
#define REP(i,num,n) for(ll i=num, i##_len=(n); i<i##_len; ++i)
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<class T> inline void add(T &a, T b){a = ((a+b) % MOD + MOD) % MOD;};
#define print(x) cout << (x) << endl;
#define pb push_back
#define mp make_pair
#define sz(x) int(x.size())
#define fs first
#define sc second
 
template<typename T>
T gcd(T a,T b){return b?gcd(b,a%b):a;}

const int INF = 1e9;
const ll LLINF = 1e16;
 
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 U,typename... V>
typename enable_if<is_same<T, U>::value!=0>::type
fill_v(U &u,const V... v){u=U(v...);}
 
template<typename T,typename U,typename... V>
typename enable_if<is_same<T, U>::value==0>::type
fill_v(U &u,const V... v){
  for(auto &e:u) fill_v<T>(e,v...);
}
 
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, -1, 1, -1};
 
template<typename T>
T lcm(T a, T b) {
    return a * b / gcd(a, b);
}

// 割り算の切り上げ処理
template<typename T>
T round_up(T a, T b) {
  return (a + b - 1) / b;
}


using pint = pair<int, int>;
using pll = pair<ll, ll>;


int main(void)
{
    cout.tie(0);
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    //auto dp=make_v<int>(4,h,w);
    //fill_v(dp,0);
    string s;
    cin >> s;
    bool sflag = false;
    bool nflag = false;
    bool eflag = false;
    bool wflag = false;
    rep(i,n){
        if(sflag && s[i] != 'S' && s[i] != N){
            print("No");
            return 0;
        }
        if(nflag && s[i] != 'S' && s[i] != N){
            print("No");
            return 0;
        }
        if(eflag && s[i] != 'E' && s[i] != W){
            print("No");
            return 0;
        }
        if(wflag && s[i] != 'E' && s[i] != W){
            print("No");
            return 0;
        }
        if(s[i] == 'S') sflag = true;
        if(s[i] == 'N') nflag = true;
        if(s[i] == 'E') eflag = true;
        if(s[i] == 'W') wflag = true;
    }
    print("Yes");
}


Compiler output:
a.cc: In function 'int main()':
a.cc:78:11: error: 'n' was not declared in this scope
   78 |     rep(i,n){
      |           ^
a.cc:9:39: note: in definition of macro 'rep'
    9 | #define rep(i,n) for(ll i=0, i##_len=(n); i<i##_len; ++i)
      |                                       ^
a.cc:79:44: error: 'N' was not declared in this scope
   79 |         if(sflag && s[i] != 'S' && s[i] != N){
      |                                            ^
a.cc:83:44: error: 'N' was not declared in this scope
   83 |         if(nflag && s[i] != 'S' && s[i] != N){
      |                                            ^
a.cc:87:44: error: 'W' was not declared in this scope
   87 |         if(eflag && s[i] != 'E' && s[i] != W){
      |                                            ^
a.cc:91:44: error: 'W' was not declared in this scope
   91 |         if(wflag && s[i] != 'E' && s[i] != W){
      |                                            ^