hdu 2837 Calculation

公式：a^b%p=a^(b%phi(p)+phi(p))%p   b>=phi(p)

#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<iomanip>
#include<cmath>
#include<string>
#include<vector>
#define ll __int64
using namespace std;
ll euler(int n)
{
    ll ans=1;
    for(int i=2;i*i<=n;i++)
    {
        if(n%i==0)
        {
            ans*=i-1;
            n/=i;
            while(n%i==0)
            {
                ans*=i;
                n/=i;
            }
        }
    }
    if(n>1) ans*=n-1;
    return ans;
}
ll pows(ll a,ll b,ll m)
{
    ll ans=1;
    while(b)
    {
        if(b&1) ans=(ans*a)%m;
        b>>=1;
        a=(a*a)%m;
    }
    return ans%m;
}
ll cmp(int a,int b,int m)
{
    ll ans=1;
    for(int i=1;i<=b;i++)
    {
        ans*=a;
        if(ans>=m) return ans;
    }
    return ans;
}
ll fun(int n,int m)
{
    ll phi=euler(m);
    if(n<10) return n;
    ll a=fun(n/10,phi);
    ll b=cmp(n%10,a,m);
    if(b>=m) 
    {
        ll ans=pows(n%10,a+phi,m);
        if(ans==0)
            ans+=m;
        return ans;
    }
    return b;
}
int main()
{
    int t,i,j,m,n;
    cin>>t;
    while(t--)
    {
        cin>>n>>m;
        ll ans=fun(n,m)%m;
        printf("%I64d
",ans);
    }
    return 0;
}