【HDU】2138 How many prime numbers

#include <cstdio>
using namespace std;
typedef long long ll;
ll ipow(ll a, ll b, ll m) { ll x=1; for(; b; b>>=1, (a*=a)%=m) if(b&1) (x*=a)%=m; return x; }
ll rand(ll a, ll b) {
	static const ll M=1e9+7, g=460353133;
	static ll now=1283901ll;
	return a+((now*=g)%=M)%(b-a+1);
}
bool check(ll x) {
	if(x==2 || x==3 || x==5 || x==7 || x==11 || x==13) return 1;
	if(x<2 || (x&1)==0 || (x%3)==0 || (x%5)==0 || (x%7)==0 || (x%11)==0 || (x%13)==0) return 0;
	int cnt=0;
	ll d=x-1; while((d&1)==0) d>>=1, ++cnt;
	for(int T=1; T<=50; ++T) {
		int a=rand(2, x-1);
		ll t=ipow(a, d, x), pre;
		for(int i=1; i<=cnt; ++i) { pre=t; (t*=t)%=x; if(t==1 && pre!=1 && pre!=x-1) return 0; }
		if(t!=1) return 0;
	}
	return 1;
}
int main() {
	int n;
	while(~scanf("%d", &n)) {
		int ans=0;
		for(int i=1; i<=n; ++i) { int a; scanf("%d", &a); if(check(a)) ++ans; }
		printf("%d\n", ans);
	}
	return 0;
}