Language: C++

#include <bits/stdc++.h>
//---------------------------
using namespace std;
//---------------------------
#define REP(i, n) for (int i = 0; i < (n); i++)
#define P(x) cout << (x) << "\n"
#define fcout cout << fixed << setprecision(18)

#define MOD 1000000007 // 1e9+7
#define PI 3.1415926535
/*
3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679
*/
#define ll long long int         // 10^18
#define INF 1000000001           // 1e9+1
#define LINF 1000000000000000001 // 1e18+1

int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};
//---------------------------

int main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    // ifstream in("input.txt");
    // cin.rdbuf(in.rdbuf());
    
    string s;cin>>s;
    if(s.size() < 4){
        P("No");
        return 0;
    }
    if(s.substr(0,4)=='YAKI'){
        P("Yes");
        return 0;
    }
    P("No");
    return 0;
}

Compiler output:
a.cc:34:23: warning: multi-character character constant [-Wmultichar]
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
a.cc: In function 'int main()':
a.cc:34:21: error: no match for 'operator==' (operand types are 'std::__cxx11::basic_string<char>' and 'int')
   34 |     if(s.substr(0,4)=='YAKI'){
      |        ~~~~~~~~~~~~~^~~~~~~~
      |                |      |
      |                |      int
      |                std::__cxx11::basic_string<char>
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:1:
/usr/include/c++/14/bits/regex.h:1103:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1103 |     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1103:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
/usr/include/c++/14/bits/regex.h:1199:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1199 |     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1199:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
/usr/include/c++/14/bits/regex.h:1274:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1274 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1274:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
/usr/include/c++/14/bits/regex.h:1366:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1366 |     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1366:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
/usr/include/c++/14/bits/regex.h:1441:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1441 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1441:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
/usr/include/c++/14/bits/regex.h:1534:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1534 |     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1534:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
/usr/include/c++/14/bits/regex.h:1613:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1613 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1613:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
/usr/include/c++/14/bits/regex.h:2186:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator==(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2186 |     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2186:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1033:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator==(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1033 |     operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1033:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::pair<_T1, _T2>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:441:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  441 |     operator==(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:441:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
/usr/include/c++/14/bits/stl_iterator.h:486:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  486 |     operator==(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:486:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1667 |     operator==(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1667:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1737 |     operator==(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1737:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
In file included from /usr/include/c++/14/bits/char_traits.h:42,
                 from /usr/include/c++/14/string:42,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/postypes.h:192:5: note: candidate: 'template<class _StateT> bool std::operator==(const fpos<_StateT>&, const fpos<_StateT>&)'
  192 |     operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:192:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::fpos<_StateT>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
In file included from /usr/include/c++/14/string:43:
/usr/include/c++/14/bits/allocator.h:235:5: note: candidate: 'template<class _T1, class _T2> bool std::operator==(const allocator<_CharT>&, const allocator<_T2>&)'
  235 |     operator==(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:235:5: note:   template argument deduction/substitution failed:
a.cc:34:23: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::allocator<_CharT>'
   34 |     if(s.substr(0,4)=='YAKI'){
      |                       ^~~~~~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54:
/usr/include/c++/14/string_view:629:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  629 |     operator==(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view