concatenate int value from vector to long long int

[Ramees219]

how can i concatenate value from a int vector to long long int i found a way i don't know it is the good way or not

#include <iostream>
#include <vector>


using namespace std;


int main(){

	vector<int> a = { 4, 5, 8, 7, 4, 5, 1 };

	long long int g = 0;
	const int Cn = 10;
	int x = 0;
	int szii = a.size();
	for (int i = 0; i < szii; i++){

		if (i == 0){

			g = a[i];

		}
		else
		{
			x = a[i];
			g = Cn * g + x;
		}

	}

	return 0;
}