Problem p03261 (C++)

Buggy submission (status: Runtime Error):
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <type_traits>
#include <typeindex>
#include <unordered_map>
#include <unordered_set>
#endif
using namespace std;
typedef long long int ll;
typedef long double ld;
typedef vector<ll> vi;
typedef vector<string> vs;
typedef pair<ll, ll> P;
typedef vector<P> vp;
#define REP(i, n) for (int i = 0; i < n; i++)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define REPR(i, n) for (int i = n - 1; i >= 0; i--)
#define FORR(i, n, m) for (int i = n - 1; i >= m; i--)
#define all(in) in.begin(), in.end()
#define ALL(in, K) in, in + K
#define INF 1e18
#define MOD 100000007
#define SIZE 10005
#define PI 3.14159265358979323846

template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
  std::fill((T *)array, (T *)(array + N), val);
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  static string str[1000];
  REP(i, n) cin >> str[i];
  REP(i, n) {
    if (str[i - 1][str[i - 1].size() - 1] != str[i][0] && i > 0) {
      // cout << str[i-1][str[i-1].size()-1] << ":" << str[i][0] << endl;
      cout << "No" << endl;
      return 0;
    }
    REP(j, i) {
      // cout << str[j] << ":" << str[i] << endl;
      if (str[i] == str[j]) {
        cout << "No" << endl;
        return 0;
      }
    }
  }
  cout << "Yes" << endl;
  return 0;
}

Fixed submission:
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <type_traits>
#include <typeindex>
#include <unordered_map>
#include <unordered_set>
#endif
using namespace std;
typedef long long int ll;
typedef long double ld;
typedef vector<ll> vi;
typedef vector<string> vs;
typedef pair<ll, ll> P;
typedef vector<P> vp;
#define REP(i, n) for (int i = 0; i < n; i++)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define REPR(i, n) for (int i = n - 1; i >= 0; i--)
#define FORR(i, n, m) for (int i = n - 1; i >= m; i--)
#define all(in) in.begin(), in.end()
#define ALL(in, K) in, in + K
#define INF 1e18
#define MOD 100000007
#define SIZE 10005
#define PI 3.14159265358979323846

template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
  std::fill((T *)array, (T *)(array + N), val);
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  static string str[1000];
  REP(i, n) cin >> str[i];
  REP(i, n) {
    // cout << str[i-1][str[i-1].size()-1] << ":" << str[i][0] << endl;
    if (i > 0)
      if (str[i - 1][str[i - 1].size() - 1] != str[i][0]) {
        cout << "No" << endl;
        return 0;
      }
    REP(j, i) {
      // cout << str[j] << ":" << str[i] << endl;
      if (str[i] == str[j]) {
        cout << "No" << endl;
        return 0;
      }
    }
  }
  cout << "Yes" << endl;
  return 0;
}