bool isNot[N];int prime[N],cnt_prime;void make_prime(){    isNot[0]=1;    isNot[1]=1;    for(int i=2; i<=N; i++)    {        if(!isNot[i])        {            prime[cnt_prime++]=i;            for(int j=2; i*j<=N; j++)                isNot[i*j]=1;        }    }}