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

const int N = 2e8 + 5;

bool table[N];
void init() {
    for (size_t i = 0; i < N; ++i) {
        table[i] = true;
    }
}

void sieve() {
    init();
    table[0] = table[1] = false;
    for (size_t div = 2; div * div <= N; div++) {
        if (table[div]) {
            for (size_t mult = div * div; mult < N; mult += div) {
                table[mult] = false;
            }
        }
    }
}

bool isComp[N];
int primes[N / 10], cnt = 0;

void clear() {
    cnt = 0;
    for (int i = 0; i < N; ++i) {
        isComp[i] = false;
    }
}


void linear_sieve() {
    clear();

    for (int i = 2; i < N; ++i) {
        if (!isComp[i])
            primes[++cnt] = i;
        for (int j = 1; primes[j] * i < N; ++j) {
            isComp[primes[j] * i] = true;
            if (i % primes[j] == 0)
                break;
        }
    }
}

void solve() {
    sieve();
    linear_sieve();
}

int main() {
    int tt = 2;
    while (tt--)
        solve();
}

>> main
  >> solve()
    >> sieve()
      >> init()
      << init(): 28.065 ms
    << sieve(): 905.288 ms
    >> linear_sieve()
      >> clear()
      << clear(): 15.414 ms
    << linear_sieve(): 453.257 ms
  << solve(): 1.359 s
  >> solve()
    >> sieve()
      >> init()
      << init(): 4.098 ms
    << sieve(): 849.913 ms
    >> linear_sieve()
      >> clear()
      << clear(): 6.121 ms
    << linear_sieve(): 440.210 ms
  << solve(): 1.290 s
<< main: 2.649 s

g++ -std=c++23 -O2 -g -Wall \
    -finstrument-functions \
    -finstrument-functions-exclude-file-list=/bits/stl,debug.h \ #example 
    solution.cpp profiler.cpp -o prof
./prof < in.txt > out.txt          # profile appears on stderr