Language: C++

#include <stdio.h>
#include <iostream>

#include <bits/stdc++.h>


using namespace std;

#define INPUT_INT(valName) int valName; cin >> valName
#define INPUT_LLINT(valName) long long int valName; cin >> valName;
#define INPUT_STR(valName) string valName; cin >> valName;
#define INPUT_LINE(valName) string valName; getline(cin,s);
#define INPUT_VECTOR_INT(valName, N) vector<int> valName(N); for(int i=0; i < N; ++i) { cin >> valName[i]; }
#define INPUT_VECTOR_DOUBLE(valName, N) vector<double> valName(N); for(int i=0; i < N; ++i) { cin >> valName[i]; }

#define OUTPUT(A) cout << (A) << endl;
#define OUTPUT2(A, B) cout << (A) << " " << (B) << endl;
#define OUTPUT3(A, B, C) cout << (A) << " " << (B) << " " << (C) << endl;

#define REP(valName, N) for(int valName = 0; valName < N; ++valName)

vector<string> split(const string& str, char delimiter) {
	vector<string> ret;
	string tmp = "";
	for (auto c : str) {
		if (c != delimiter) {
			tmp.push_back(c);
		} else {
			ret.push_back(tmp);
			tmp = "";
		}
	}
	ret.push_back(tmp);
	return ret;
}

template <typename T> void sortAsc(vector<T>& v) { sort(v.begin(), v.end(), less<T>()); }
template <typename T> void sortDesc(vector<T>& v) { sort(v.begin(), v.end(), greater<T>()); }

template <typename T> void insert(vector<T>& dest, const vector<T>& src) { copy(src.begin(), src.end(), back_inserter(dest)); }

template <long long int MOD> long long int mod_inv(long long int a) {
	long long b = MOD, u = 1, v = 0;
	while (b) {
		long long int t = a / b;
		a -= t * b; swap(a, b);
		u -= t * v; swap(u, v);
	}
	u %= MOD;
	if (u < 0) u += MOD;
	return u;
}

template <long long int MOD> long long int mod_add(long long int a, long long int b) {
	return (a + b) % MOD;
}

template <long long int MOD> long long int mod_sum(long long int a, long long int b) {
	return (a - b) % MOD;
}

template <long long int MOD> long long int mod_mul(long long int a, long long int b) {
	return (a % MOD) * (b % MOD) % MOD;
}

template <long long int MOD> long long int mod_mul(long long int a, long long int b, long long int c) {
	return mod_mul<MOD>(a, mod_mul<MOD>(b, c));
}

template <long long int MOD> long long int mod_div(long long int a, long long int b) {
	return (a % MOD) * mod_inv<MOD>(b) % MOD;
}


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

map< int64_t, int > prime_factor(int64_t n) {
	map< int64_t, int > ret;
	for (int64_t i = 2; i * i <= n; i++) {
		while (n % i == 0) {
			ret[i]++;
			n /= i;
		}
	}
	if (n != 1) ret[n] = 1;
	return ret;
}

int main() {
	
	// TODO: streamやめる

	cin.tie(0); ios::sync_with_stdio(false);

	INPUT_LLINT(N);

	auto P = prime_factor(N);

	unsigned long long int n = 400000000;

	unsigned long long int a = 1;
	unsigned long long int b = 1;
	for (auto p = P.rbegin; p != P.rend(); ++p) {
		while (p.second--) {
			if ((a * p.first) + b < a + (b * p.first)) {
				a *= p.first;
			} else {
				b *= p.first;
			}
		}
	}
	
	OUTPUT(a + b - 2);

	return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:103:25: error: unable to deduce 'auto' from 'P.std::map<long int, int>::rbegin'
  103 |         for (auto p = P.rbegin; p != P.rend(); ++p) {
      |                       ~~^~~~~~
a.cc:103:25: note:   couldn't deduce template parameter 'auto'
  103 |         for (auto p = P.rbegin; p != P.rend(); ++p) {
      |                         ^~~~~~