BZOJ 4459: [Jsoi2013]丢番图 数学推导

之前绝对做过几乎一模一样的题，现在做竟然忘了.

code:

#include <bits/stdc++.h>
#define ll long long
#define setIO(s) freopen(s".in","r",stdin)
using namespace std;
ll n,ans=1;
int main()
{
    // setIO("input");
    ll i,j;
    scanf("%lld",&n);
    for(i=2;i*i<=n;++i)
    {
        if(n%i==0)
        {
            ll sum=0;
            while(n%i==0) ++sum,n/=i;
            ans*=2*sum+1;
        }
    }
    if(n>1)  ans*=3;
    printf("%lld\n",(ans+1)/2);
    return 0;
}