Cod sursa(job #3348154)

Utilizator Radu_BicliBiclineru Radu Radu_Bicli Data 20 martie 2026 08:51:50
Problema Frac Scor 50
Compilator cpp-64 Status done
Runda Arhiva de probleme Marime 1.3 kb
#include <bits/stdc++.h>

using namespace std;

#define USE_STD_IO 0
#if USE_STD_IO
    #define fin cin
    #define fout cout
#else
    ifstream fin("frac.in");
    ofstream fout("frac.out");
#endif // USE_STD_IO

int n, p, fact[102], nrp;

static inline void DescFactPrimi(int n) {
    int d = 2;
    while(1 < n) {
        if(0 == n % d) {
            fact[++nrp] = d;
            while(0 == n % d) n /= d;
        }
        d += 1 + (d & 1);
    }
}

static inline int CatePrime(int n) {
    int nr = 0;
    for(int i = (1 << nrp) - 1; i >= 1; i--) {
        int prod = 1;
        int biti = 0;
        for(int j = 0; j < nrp; j++) {
            if(i >> j & 1) {
                biti++;
                prod *= fact[j + 1];
            }
        }
        if(biti & 1) nr += n / prod;
        else         nr -= n / prod;
    }
    return n - nr;
}

int main() {
    if(USE_STD_IO) ios_base::sync_with_stdio(false);
    fin.tie(NULL);
    fout.tie(NULL);

    fin >> n >> p;
    DescFactPrimi(n);

    int st = 1, dr = 1e9;
    int mij, poz = dr;
    while(st <= dr) {
        int mij = st + (dr - st) / 2;
        if(p <= CatePrime(mij)) {
            poz = mij;
            dr = mij - 1;
        }
        else st = mij + 1;
    }
    fout << poz;

    return 0;
}