foo.cpp: In function 'long int commonMultiple(long int, long int)':
foo.cpp:22:21: error: expression cannot be used as a function
 return (a/div)(b/div)div;
                     ^
foo.cpp:22:22: error: expected ';' before 'div'
 return (a/div)(b/div)div;
                      ^
foo.cpp:22:25: warning: statement has no effect [-Wunused-value]
 return (a/div)(b/div)div;
                         ^
foo.cpp: In function 'int main()':
foo.cpp:36:22: error: expected ')' before 'x'
 if(commonDivisor(div x, div y) == div && commonMultiple(div x, div y) == mul)
                      ^
foo.cpp:36:29: error: expected ')' before 'y'
 if(commonDivisor(div x, div y) == div && commonMultiple(div x, div y) == mul)
                             ^
foo.cpp:36:61: error: expected ')' before 'x'
 if(commonDivisor(div x, div y) == div && commonMultiple(div x, div y) == mul)
                                                             ^
foo.cpp:36:68: error: expected ')' before 'y'
 if(commonDivisor(div x, div y) == div && commonMultiple(div x, div y) == mul)
                                                                    ^
foo.cpp: In function 'long int commonMultiple(long int, long int)':
foo.cpp:23:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^