View Compilation Error

0_0_26099661_17705.cpp:5:7: error: expected nested-name-specifier before 'namesapce'
 using namesapce std;
       ^
0_0_26099661_17705.cpp: In function 'int main()':
0_0_26099661_17705.cpp:17:15: error: 'GCD' was not declared in this scope
   gcd=GCD(e,fn);
               ^