fzu1759 Super A^B mod C 扩展欧拉定理降幂

扩展欧拉定理：

\[a^x \equiv a^{x\mathrm{\ mod\ }\varphi(p) + x \geq \varphi(p) ? \varphi(p) : 0}(\mathrm{\ mod\ }p)
\]

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
typedef long long ll;
ll aa, cc;
char bb[1000005];
ll getPhi(ll x){
	ll ans=x;
	for(ll i=2; i*i<=x; i++)
		if(x%i==0){
			ans -= ans / i;
			while(x%i==0)	x /= i;
		}
	if(x>1)	ans -= ans / x;
	return ans;
}
ll ksm(ll a, ll b, ll c){
	ll re=1;
	while(b){
		if(b&1)	re = (re * a) % c;
		a = (a * a) % c;
		b >>= 1;
	}
	return re;
}
int main(){
	while(scanf("%lld %s %lld", &aa, bb, &cc)!=EOF){
		ll phi=getPhi(cc);
		int len=strlen(bb);
		ll tmp=0;
		for(int i=0; i<len; i++){
			tmp = tmp * 10 + bb[i] - '0';
			if(tmp>=phi)	break;
		}
		if(tmp>=phi){
			tmp = 0;
			for(int i=0; i<len; i++)
				tmp = (tmp * 10 + bb[i] - '0') % phi;
			printf("%lld\n", ksm(aa, tmp+phi, cc));
		}
		else	printf("%lld\n", ksm(aa, tmp, cc));
	}
	return 0;
}