Scope of Multiple variables

Supposedly , there are multiple variables (with same name) in different scopes. Now , if i want to access multiple variables (with same name ) , how do i do that?

Ex :

(assume all header files included)

int y=10;

int main()
{

int y=100;

for(int z=0;z<6;z++)
{

int y;

cin>>y;

cout<<::y+y; <------- Here if i wanted to use the variable y with global scope . Then how should i do it ?

}

here it is using the global y only, within one function you can only have one scope used for the variable

i.e one variable cannot have overlapping local scopes