POJ 2447 RSA

#include <cstdio>
#include <cstring>
#include <iostream>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <queue>
#include <stack>
#include <string>
#include <vector>
#define oo (1<<28)
#define gcc 121232
using namespace std;
typedef long long LL;
LL gcd(LL a,LL b)
{
    return b==0?a:gcd(b,a%b);
}
LL ext_gcd(LL a,LL b,LL &x,LL &y)
{
    if(!b){
        x=1;y=0;return a;
    }
    LL d=ext_gcd(b,a%b,y,x);
    y-=a/b*x;
    return d;
}
LL Mul(LL a,LL b,LL m)
{
    LL r=0;
    while(b)
    {
        if(b&1) r=(r+a)%m;
        a=(a<<1)%m;
        b>>=1;
    }
    return r;
}
LL power(LL a,LL b,LL m)
{
    LL r=1;
    while(b)
    {
        if(b&1) r=Mul(r,a,m);
        a=Mul(a,a,m);
        b>>=1;
    }
    return r;
}
LL pollard_rho(LL n)
{
    LL x,y,d,i=1,k=2;
    x=rand()%(n-1)+1;
    y=x;
    while(true)
    {
        ++i;
        x=((Mul(x,x,n)-gcc)%n+n)%n;
        d=gcd(y-x+n,n);
        if(d>1&&d<n) return d;
        if(x==y) return n;
        if(i==k)
            y=x,k<<=1;
    }
}
int main()
{
    LL c,e,n;
    while(~scanf("%I64d%I64d%I64d",&c,&e,&n))/// n 2 ， pollard_rho 
    {
        LL p=pollard_rho(n),q=n/p;
        LL t=(p-1)*(q-1);
        LL x,d;
        ext_gcd(e,t,d,x);/// e t 
        d=(d%t+t)%t;
        printf("%I64d
",power(c,d,n));
    }
    return 0;
}