Largest prime factor(素数表的巧用）

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<iostream>#include<iostream>#include<vector>#define Max 1000006using namespace std;int vis[Max];int n;void make_prime(){pair<int,int>p;memset(vis,0,sizeof(vis));int i,j,num=1;for(i=2;i<Max;i++){if(!vis[i]){vis[i]=num;for(j=i+i;j<Max;j+=i)vis[j]=num;num++;}}}int main(){//freopen("b.txt","r",stdin);make_prime();while(scanf("%d",&n)==1)printf("%d\n",vis[n]);return 0;}