PE 3 Largest prime factor

#include<iostream>using namespace std;int prime(long int i){for(long int j=2;j*j<=i;j++){if(i%j==0)return 1;}return 0;}int main(void){__int64  n=600851475143 ;long int j=-1;long int i;long int *s;s=new long int [1000001];   // memset(s,0,sizeof(s));for(i=2;i*i<=n;i++){if(n%i==0&&prime(i)==0){j++;s[j]=i;}}cout<<s[j];return 0;}