Language: C++

#include <bits/stdc++.h>
using namespace std;

#define int long long
#define vvi vector<vector<int>>
#define vec vector
#define pq priority_queue
#define all(v) (v).begin(), (v).end()
#define uniqueV(x) sort(x.begin(), x.end()); x.erase(unique(x.begin(), x.end()), x.end());
#define rep(i, n) for (int (i) = (0); (i) < (n); ++(i))
#define repp(i, m, n) for (int (i) = (m); (i) < (n); ++(i))
#define dbg(x) cerr << #x << ": " << x << endl;
#define dbg2(x, y) cerr<<"("<<#x<<", "<<#y<<") = "<<"("<<x<<", "<<y<<")"<<endl;
#define dbg3(x, y, z) cerr<<"("<<#x<<", "<<#y<<", "<<#z<<") = "<<"("<<x<<", "<<y<<", "<<z<<")"<<endl;
#define dbgB(value, size) cerr<<#value<<": "<<bitset<size>(value) << endl;
#define line() cerr << "---------------" << endl;

const int dx[] = {1, -1, 0, 0};
const int dy[] = {0, 0, -1, 1};
const double PI = 3.14159265358979323846;

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<typename T>
void print1(T begin, T end) {
  while (begin != end) {
    cerr << (*begin) << " ";
    *begin++;
  }
  cerr << endl;
}

template<typename T>
void print2(T Array, int height, int width) {
  for (int i = 0; i < height; i++) {
    for (int j = 0; j < width; j++) {
      cerr << " " << Array[i][j];
    }
    cerr << endl;
  }
}

void print() { std::cerr << endl; }
template <class Head, class... Tail>
void print(Head&& head, Tail&&... tail) {
  std::cerr << head << " ";
  print(std::forward<Tail>(tail)...);
}

template<class T>
void Add(T &a, const T &b, const T &mod=1000000007) {
  int val = ((a % mod) + (b % mod)) % mod;
  if (val < 0) { val += mod; }
  a = val;
}

template <typename X, typename T> auto vectors(X x, T a) { return vector<T>(x, a); }
template <typename X, typename Y, typename Z, typename... Zs> auto vectors(X x, Y y, Z z, Zs... zs) { auto cont = vectors(y, z, zs...); return vector<decltype(cont)>(x, cont); }

// ------------------------------------------------------------------------------------------

string s;

signed main() {
  cin >> s;

  int ans = 1e18;
  rep (i, s.size()) {
    int a = stoi(s.substr(i, 3));
    if (s.substr(i, 3) != 3) continue;
    chmin(ans, abs(a - 753));
  }

  cout << ans << endl;

  return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:71:24: error: no match for 'operator!=' (operand types are 'std::__cxx11::basic_string<char>' and 'int')
   71 |     if (s.substr(i, 3) != 3) continue;
      |         ~~~~~~~~~~~~~~ ^~ ~
      |                 |         |
      |                 |         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:1132:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator!=(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1132 |     operator!=(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1132:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
/usr/include/c++/14/bits/regex.h:1212:5: 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>&)'
 1212 |     operator!=(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1212:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
/usr/include/c++/14/bits/regex.h:1305:5: 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>&)'
 1305 |     operator!=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1305:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
/usr/include/c++/14/bits/regex.h:1379:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1379 |     operator!=(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1379:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
/usr/include/c++/14/bits/regex.h:1473:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1473 |     operator!=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1473:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
/usr/include/c++/14/bits/regex.h:1547:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1547 |     operator!=(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1547:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'int'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
/usr/include/c++/14/bits/regex.h:1647:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator!=(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1647 |     operator!=(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1647:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
/usr/include/c++/14/bits/regex.h:2213:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator!=(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2213 |     operator!=(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2213:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
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:1052:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator!=(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1052 |     operator!=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1052:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::pair<_T1, _T2>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:455:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  455 |     operator!=(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:455:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
/usr/include/c++/14/bits/stl_iterator.h:500:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  500 |     operator!=(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:500:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1686 |     operator!=(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1686:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator!=(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1753 |     operator!=(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1753:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::move_iterator<_IteratorL>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
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:197:5: note: candidate: 'template<class _StateT> bool std::operator!=(const fpos<_StateT>&, const fpos<_StateT>&)'
  197 |     operator!=(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/postypes.h:197:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::fpos<_StateT>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
In file included from /usr/include/c++/14/string:43:
/usr/include/c++/14/bits/allocator.h:243:5: note: candidate: 'template<class _T1, class _T2> bool std::operator!=(const allocator<_CharT>&, const allocator<_T2>&)'
  243 |     operator!=(const allocator<_T1>&, const allocator<_T2>&)
      |     ^~~~~~~~
/usr/include/c++/14/bits/allocator.h:243:5: note:   template argument deduction/substitution failed:
a.cc:71:27: note:   'std::__cxx11::basic_string<char>' is not derived from 'const std::allocator<_CharT>'
   71 |     if (s.substr(i, 3) != 3) continue;
      |                           ^
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:651:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator!=(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  651 |     operator!=(basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:651:5: note:   template argument deduction/s