ACM2136

/*
Problem Description
Everybody knows any number can be combined by the prime number.
Now, your task is telling me what position of the largest prime factor.
The position of prime 2 is 1, prime 3 is 2, and prime 5 is 3, etc.
Specially, LPF(1) = 0.
 

Input
Each line will contain one integer n(0 < n < 1000000).
 

Output
Output the LPF(n).
 

Sample Input
1
2
3
4
5
 

Sample Output
0
1
2
1
3
*/
#include <stdio.h>
#include <string.h>

const int N = 1000000;
int hash[N+5];
int prime[N+5];

void sushu()
{
    int  i,j;
    memset(prime,0,sizeof(prime));
    hash[1] = 0;
    int flag = 0;
    for(i = 2; i<=N; i++)
    {
        if(!prime[i])
        {
            hash[i] = ++flag;
            for(j = i; j<=N; j+=i)
            {
                prime[j] = i;
            }
        }
    }
}

int main()
{
    int i;
    memset(hash,0,sizeof(hash));
    sushu();
    while(~scanf("%d",&i))
    {
        if(i == 1)
        printf("0\n");
        else
        {
            int k = prime[i];
            printf("%d\n",hash[k]);
        }
    }

    return 0;
}