Language: C++

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(ll i = 0; i < (ll)(n); i++)
#define rep2(i, a, n) for(ll i = a; i < (ll)(n); i++)
#define memi cout << endl
#define kono(n) cout << fixed << setprecision(n)
#define all(c) (c).begin(), (c).end()
#define pb push_back
#define hina cout << ' '
#define in(n) cin >> n
#define in2(n, m) cin >> n >> m
#define in3(n, m, l) cin >> n >> m >> l
#define out(n) cout << n
const ll mei = (ll)1e9 + 7;

int main(){
  ll a = 0;
  string s;
  in(s);
  ll n;
  while(s.size() > 4){
    n = s.size();
    if(s[n - 1] == 'm' && s[n - 2] == 'a' && s[n - 3] == 'e' && s[n - 4] == 'r' && s[n - 5] == 'd'){
      rep(i, 5)
        s.pop_back();
    }
    else if(s[n - 1] == 'e' && s[n - 2] == 's' && s[n - 3] == 'a' && s[n - 4] == 'r' && s[n - 5] == 'e'){
      rep(i, 5)
        s.pop_back();
    }
    else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      rep(i, 7)
        s.pop_back();
    }
    else if(n >= 6 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 's' && s[n - 4] == 'a' && s[n - 5] == 'r' && s[n - 6] == 'e'){
      rep(i, 6)
        s.pop_back();
    }
    else break;
    if(s.size() == 0)
      a = 1;
  }
  if(a == 1)
    out("YES");
  else
    out("NO");
  memi;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:32:141: error: no match for 'operator-' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'int')
   32 |     else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      |                                                                                                                                           ~ ^ ~
      |                                                                                                                                           |   |
      |                                                                                                                                           |   int
      |                                                                                                                                           std::string {aka std::__cxx11::basic_string<char>}
In file included from /usr/include/c++/14/bits/stl_algobase.h:67,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_iterator.h:618:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__y.base() - __x.base())) std::operator-(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  618 |     operator-(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:618:5: note:   template argument deduction/substitution failed:
a.cc:32:143: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::reverse_iterator<_Iterator>'
   32 |     else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      |                                                                                                                                               ^
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr decltype ((__x.base() - __y.base())) std::operator-(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1790 |     operator-(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1790:5: note:   template argument deduction/substitution failed:
a.cc:32:143: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::move_iterator<_IteratorL>'
   32 |     else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      |                                                                                                                                               ^
In file included from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127:
/usr/include/c++/14/complex:370:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const complex<_Tp>&)'
  370 |     operator-(const complex<_Tp>& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:370:5: note:   template argument deduction/substitution failed:
a.cc:32:143: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::complex<_Tp>'
   32 |     else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      |                                                                                                                                               ^
/usr/include/c++/14/complex:379:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&, const _Tp&)'
  379 |     operator-(const complex<_Tp>& __x, const _Tp& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:379:5: note:   template argument deduction/substitution failed:
a.cc:32:143: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::complex<_Tp>'
   32 |     else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      |                                                                                                                                               ^
/usr/include/c++/14/complex:388:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const _Tp&, const complex<_Tp>&)'
  388 |     operator-(const _Tp& __x, const complex<_Tp>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/complex:388:5: note:   template argument deduction/substitution failed:
a.cc:32:143: note:   mismatched types 'const std::complex<_Tp>' and 'int'
   32 |     else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      |                                                                                                                                               ^
/usr/include/c++/14/complex:465:5: note: candidate: 'template<class _Tp> std::complex<_Tp> std::operator-(const complex<_Tp>&)'
  465 |     operator-(const complex<_Tp>& __x)
      |     ^~~~~~~~
/usr/include/c++/14/complex:465:5: note:   candidate expects 1 argument, 2 provided
In file included from /usr/include/c++/14/valarray:605,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:166:
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:32:143: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   32 |     else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      |                                                                                                                                               ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:32:143: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   32 |     else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      |                                                                                                                                               ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:32:143: note:   mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
   32 |     else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      |                                                                                                                                               ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray<typename _Dom::value_type>&)'
  406 |     _DEFINE_EXPR_BINARY_OPERATOR(-, struct std::__minus)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/valarray_after.h:406:5: note:   template argument deduction/substitution failed:
a.cc:32:143: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
   32 |     else if(n >= 7 && s[n - 1] == 'r' && s[n - 2] == 'e' && s[n - 3] == 'm' && s[n - 4] == 'a' && s[n - 5] == 'e' && s[n - 6] == 'r' && s[s - 7] == 'd'){
      |                                                                                                                                               ^
/usr/include/c++/14/bits/valarray_after.h:406:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__minus, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__minus, typename _Dom1::value_type>::result_type> std::operator-(const valarray<typename _Dom::value_type