рандом

#include <iostream>
#include <vector>
#include <algorithm>
#include <fstream>
#include <functional>
#include <cmath>
#include <set>
#include <deque>
#include <queue>
#include <utility>
#include <map>
#include <string>
#include <iomanip>
#include <cmath>
#include <utility>
#include <ctype.h>
#include <stdio.h>
#include <random>
#include <ctime>


#define mp make_pair

typedef long long ll;

using namespace std;

int main() {
    mt19937 gen(time(0));
    uniform_real_distribution<double> dist(0.0, 1.0);
    ...
    double a = dist(gen);
    double b = dist(gen);
    ...
}