A hard puzzle——快速幂

#include<iostream> #include<cstdio> #include<algorithm> #include<math.h> #include<cstring> #include<string> #include<vector> using namespace std; typedef long long ll; const int mod=1e9; ll qpow(ll a,ll b){ ll res=1; while(b){ if(b&1) res=res*a%mod; a=a*a%mod; b>>=1; } return res; } int main(){ ll a,b; while(cin>>a>>b){ ll ans=qpow(a,b); //cout<<ans<<endl; ans=ans%10; cout<<ans<<endl; } return 0; }