/in/foo.cc: In function 'long long int gcd(int, int)':
/in/foo.cc:9:2: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
  if(b==0); return a;
  ^~
/in/foo.cc:9:12: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'
  if(b==0); return a;
            ^~~~~~
/in/foo.cc:10:20: error: lvalue required as left operand of assignment
  gcd(a,b)=gcd(b,a%b)
                    ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:14:16: error: 'a' was not declared in this scope
  scanf("%d%d",&a,&b);
                ^
/in/foo.cc:14:19: error: 'b' was not declared in this scope
  scanf("%d%d",&a,&b);
                   ^