Can anyone help me to improve the code.. Here is my solution:3406918.

some somebody explain it.thanks in advance..

I know the logic is true for small numbers,but how can i prove the correctness of the algorithm for all n; here is the code:2296715

here is my solution,plz help 2269000

Your code here...

include

using namespace std; int main() { long long n,u=1,d=2,c=1000000007; cin>>n; while(n) { if(n%2) u=(u*d)%c; d=(d*d)%c; n/=2; } cout<<((u*u+u)/2)%c; return 0; }

i think the answer is (4^n-(1+2.....(2^n-1)))%(10^9+7);but upper bound of n is 10^18; so how to find the answer?

need tutorial on matrix exponential algorithm