快速幂

typedef long long LL;
LL binaryPow(LL a,LL b,LL m){
    if(b==0)return 1;
    if(b%2==1)return a*binaryPow(a,b-1,m)%m;
    else{
        LL mul=binaryPow(a, b/2,m);
        return mul*mul%m;
    }
}