Spoj/pagain.cpp at master · Jaskamalkainth/Spoj · GitHub

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/*
 *
 *    J1K7_7
 *
 */
#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <vector>
#include <deque>
#include <queue>
#include <stack>
#include <set>
#include <cstring>
#include <list>
#include <map>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <utility>
#include <bitset>
#include <cmath>
#include <ctime>
#include <cstdio>
#include <limits>
using namespace std;
typedef long long          ll;
typedef unsigned long long ull;
typedef long double        ld;
typedef pair<int,int>      pii;
typedef pair<ll,ll>        pll;
typedef vector<int>        vi;
typedef vector<long long>  vll;
#define l(x) 		       (x << 1) + 1
#define r(x) 		       (x << 1) + 2
#define mid(l, r) 	       ((l + r) >> 1)
#define mp                 make_pair
#define pb                 push_back
#define all(a)             a.begin(),a.end()
#define pr(n)              printf("%d",n)
#define s(n)               scanf("%d",&n)
#define debug(x)	       {cerr <<#x<<" = " <<x<<"\n"; }
#define debug2(x, y)       {cerr <<#x<<" = " <<x<<", "<<#y <<" = " <<y <<"\n";}
#define ss                 second
#define ff                 first
#define m0(x) 		       memset(x,0,sizeof(x))
#define snuke(c,itr)       for(__typeof((c).begin()) itr=(c).begin();itr!=(c).end();itr++)

const ll  mx_ll   = numeric_limits<ll> :: max();
const int mx_int  = numeric_limits<int> :: max();

const long double PI = (long double)(3.1415926535897932384626433832795);

inline bool ispow2(int x){return (x!=0 && (x&(x-1))==0);} //0 or 1

int msb(unsigned x){ union { double a; int b[2]; }; a = x; return (b[1] >> 20) - 1023; }

template<class T>
inline void cinarr(T a, int n){ for (int i=0;i<n;++i) cin >> a[i];}

inline ll gcd(ll a,ll b){ll t;while(b){a=a%b;t=a;a=b;b=t;}return a;}
inline ll lcm(ll a,ll b){return a/gcd(a,b)*b;}

inline int nextint(){ int x; scanf("%d",&x); return x; }
inline ll nextll(){ ll x; scanf("%lld",&x); return x; }


int b[]={2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97};
unsigned long long mod; // mod is used in Milong longer() as mod = p

inline  unsigned long long multiply( long long a, unsigned long long b)   // O(1) for (a*b)%m
{
	a %= mod;
	b %= mod;
	long double res = a;
	res *= b;
	unsigned long long c = (long long) (res / mod);
	a *= b;
	a -= c * mod;
	a %= mod;
	if (a < 0) a += mod;
	return a;
}

inline  unsigned long long power( unsigned long long a, unsigned long long b)
{
	unsigned long long ans=1;
	while(b)
	{
		if(b&1)
		{
			ans=multiply(ans,a);
		}
		a=multiply(a,a);
		b>>=1;
	}
	return ans;
}

// Milong longer(x) wi unsigned long long check if x is prime or not
// log(n)^3 n = Input Number

inline bool Miller( unsigned long long p)
{
	if(p<2)  return false;
	if(p!=2 && !(p&1)) return false;
	for(int i=0;i<25;i++)
	{
		if(p==b[i])return true;
		else if(p%b[i]==0)return false;
	}
	int count = 0;
	unsigned long long s=p-1;
	while(!(s&1))
	{
		s/=2;
		count++;
	}
	unsigned long long accuracy=2;
	for(int i=0;i<accuracy;i++)
	{
		unsigned long long a=rand()%(p-1)+1;
		mod = p;
         unsigned long long x=power(a,s);
        if(x == 1 || x == p-1) continue;
        int flag = 0;
        for(int i = 1; i < count; i++)
        {
            x = multiply(x,x);
            if(x == 1) return false;
            if(x == p-1)
            {
                flag = 1;
                break;
            }
        }
        if(flag) continue;
        return false;
    }
    return true;
}
int main()
{
    ios_base::sync_with_stdio(false); cin.tie(0);
	int t; t = nextint();
	while(t--)
	{
		ll n = nextll();
		n--;
		while(!Miller(n))
		{
			n--;
		}

		printf("%lld\n",n);
	}


    return 0;
}