C random number generator

#include "stdio.h"
#include <stdlib.h>
// This rand() function is not a good random number generator(People say so)
/*
int rand(int l, int r){
    static std::mt19937 rng(std::chrono::steady_clock::now().time_since_epoch().count());
    std::uniform_int_distribution<int> uid(l, r); return uid(rng);
}*/

signed main() {
    FILE *fptr = fopen("in", "w");

    int t = 1, n;
    // fprintf(fptr, "%d\n", t);
    for(int i = 0; i < t; ++i) {
        n = rand() % 100 + 1;
        if(i == 0) {
             fprintf(fptr, "%d\n", n);
        }
        else
            fprintf(fptr, "\n%d\n", n);
        while(n--)
            fprintf(fptr, "%d ", rand() % 100);

    }
    fclose(fptr);
}