Language: C++

#include<bits/stdc++.h>

#define ll long long
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define pll pair<long long,long long>

#define fastio() ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define endl "\n"

#define Debug(x) cout<<(#x)<<" >> "<<(x)<<endl

using namespace std;

ll fastpow(ll angka,ll pangkat,ll MOD){
	ll res=1;
	while(pangkat){
		if(pangkat&1) res=(res*angka)%MOD;
		angka=(angka*angka)%MOD;
		pangkat=pangkat>>1;
	}
	return res;
}

ll fastpow(ll angka,ll pangkat){
	ll res=1;
	while(pangkat){
		if(pangkat&1) res=(res*angka);
		angka=(angka*angka);
		pangkat=pangkat>>1;
	}
	return res;
}

ll gcd(ll angka1,ll angka2){
	while(angka2){
		swap(angka1,angka2);
		angka2=angka2%angka1;
	}
	return angka1;
}

ll lcm(ll angka1,ll angka2){
	return (angka1/gcd(angka1,angka2))*angka2;
}



void solve(){
	int n;
	cin>>n;
	
	if(n%2==0 || n%5==0){
		cout<<-1<<endl;
		return;
	}
	
	int val=0;
	int ct=0;
	while(true){
		ct++;
		val=val*10+7;
		if(val%n==0){
			cout<<ct<endl;
			return;
		}
		val=val%n;
	}
	
}

int main(){
	
	fastio();
	
	int t=1;
//	cin>>t;
	
	for(int tt=0;tt<t;tt++){
//		cout<<"Case #"<<tt+1<<": ";solve();
//		if(solve()) cout<<""<<endl;
		solve();
	}
	
	return 0;
}




Compiler output:
a.cc: In function 'void solve()':
a.cc:67:33: error: no match for 'operator<' (operand types are 'std::basic_ostream<char>' and 'const char [2]')
   67 |                         cout<<ct<endl;
      |                         ~~~~~~~~^
      |                             |
      |                             std::basic_ostream<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:1143:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1143 |     operator<(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1143:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
/usr/include/c++/14/bits/regex.h:1224:5: 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>&)'
 1224 |     operator<(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
/usr/include/c++/14/bits/regex.h:1317:5: 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>&)'
 1317 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
/usr/include/c++/14/bits/regex.h:1391:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1391 |     operator<(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'const char [2]'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
/usr/include/c++/14/bits/regex.h:1485:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1485 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
/usr/include/c++/14/bits/regex.h:1560:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1560 |     operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'const char [2]'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
/usr/include/c++/14/bits/regex.h:1660:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1660 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
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:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'const std::pair<_T1, _T2>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1694 |     operator<(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1760 |     operator<(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/string_view:673:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  673 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:673:5: note:   template argument deduction/substitution failed:
a.cc:12:14: note:   'std::basic_ostream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
   12 | #define endl "\n"
      |              ^~~~
a.cc:67:34: note: in expansion of macro 'endl'
   67 |                         cout<<ct<endl;
      |                                  ^~~~
/usr/include/c++/14/string_view:680:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, __type_identity_t<basic_string_view<_CharT, _Traits> >)'
  680 |     operator< (basic_string_view<_CharT, _Traits> _