Language: C++

#include <iostream>
#include <cmath>
#include <vector>
#include <bitset>
#include <algorithm>
#include <stack>
#include <queue>
#include <map>
#include <climits>
#include <set>
#include <map>
#include <iomanip>
#include <cassert>
#include <functional>
#include <cstring>

using namespace std;

#define mp make_pair
#define FOR(i, a, b) for(int (i)=a;(i)<(b);++(i))
#define rep(i, n)  FOR(i,0,n)
#define FFOR(i, a, b) for(int (i)=a;(i)>(b);--(i))
#define rrep(i,n) FFOR(i,0,n)
#define vsort(v) sort((v).begin(), (v).end());					//小さい順
#define rvsort(v) sort(v.begin(), v.end(),greater<>());		//大きい順
#define YES cout<<"YES"<< endl
#define NO cout<<"NO"<<endl
#define Yes cout<<"Yes"<<endl
#define No cout<<"No"<<endl  
#define yes cout<<"yes"<<endl
#define no cout<<"no"<<endl
#define all(c) (c).begin(),(c).end()
#define ll long long
#define lb long double
#define vi vector<int>
#define vvi vector<vector<int>>
#define vl vector<ll>
#define vvl vector<vector<ll>>
#define vb vector<bool>
#define vvb vector<vector<bool>>
#define vs vector<string>
#define vc vector<char>
#define vvc vector<vector<char>>
#define Print(p) cout<<(p)<<endl
#define F first
#define S second
#define pb push_back
#define mod 1000000007LL
#define INF 123456789012345
typedef pair<int, int> P;
typedef pair<int, P> PP;

const int maxn =1e5 + 10;


int main() {

	int x; cin >> x;

	int ans = 1;
	FOR(i,2,sqrt(x))
	FOR(j,2,1000)
	{
		if(pow(i,j) > x) break;
		ans = max(ans,pow(i,j));
	}

	cout << ans<<endl;
	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:65:26: error: no matching function for call to 'max(int&, __gnu_cxx::__promote<double>::__type)'
   65 |                 ans = max(ans,pow(i,j));
      |                       ~~~^~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:65:26: note:   deduced conflicting types for parameter 'const _Tp' ('int' and '__gnu_cxx::__promote<double>::__type' {aka 'double'})
   65 |                 ans = max(ans,pow(i,j));
      |                       ~~~^~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:5:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:65:26: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   65 |                 ans = max(ans,pow(i,j));
      |                       ~~~^~~~~~~~~~~~~~