快速乘

include

using namespace std;
typedef unsigned long long ull;
typedef long long ll;
ull mul(ull a,ull b,ull mod) //计算ab%mod的值
{
ull res=0,base=a%mod;
while(b)
{
if(b&1) res=(res+base)%mod;
base=(base2)%mod;;
b>>=1;
}
return res;
}
int main()
{
return 0;
}