Nefu 1151 Special Prime numbers

Special Prime number problem:1151Time Limit:1000msMemory Limit:65535KDescription

If a number is prime, and his number in the mass tables is prime, it is called a special prime. For example, the 7th prime number in the quality tables is 17, because 7 and 17 are prime numbers, so we call 17 a special prime number, such as the 10th prime number is 29, because 10 is not a prime number, so 29 is not a special prime number. Now given a nonnegative integer n, the largest special prime number of the <=n is obtained.

Input

Multiple sets of input data n (0<=n<=10^6).

Output

The output is the largest special prime number less than or equal to N, and for a given n if there is no such prime number, output-1.

Sample Input

0205060

Sample Output

-1174159

Hint Source

#include <iostream>#include<string.h>using namespacestd;#defineMAXN 1000100inti,j,n,m,a[maxn],b[maxn],k=1;voidGetprime ()//Prime number of hit table get prime number{memset (A,0,sizeof(a)); memset (b,0,sizeof(b)); b[1]=1;  for(i=2; i<maxn;i++)    {        if(!B[i]) {A[k++]=i;  for(j=i+i;j<maxn;j+=i) b[j]=1; }    }}intMain () {getprime ();  while(cin>>N) {if(n<3) {cout<<-1<<Endl; Continue; }        intflag=3;  for(i=1; i<k;i++)        {            if(!b[i])//It's a special prime number.            {                if(a[i]<=n)//mark the previous oneFlag=a[i];//you can't just output the last special prime number, you can't run to else.                Else                 Break; Note that this must not be output in else, because the last special prime number will not run into else.
I found this error with the generator in the hall, 1000 input 999 sets of output
If you want to output in else, change the MAXN to 2000100}} cout<<flag<<Endl; }        /*for (i=1;i<20;i++) {if (!b[i]) cout<< "Special prime number:";            else cout<< "";        cout<< "I:" <<i<< "" <<a[i]<<endl; }*/    return 0;}

Nefu 1151 Special prime numbers