foo.cpp: In function 'int main()':
foo.cpp:12:9: error: 'd' cannot be used as a function
 c=(d(d+1))/2;
         ^
foo.cpp:17:4: error: unable to find numeric literal operator 'operator"" a'
 e=(2a-d(d+1))/2(d+1);
    ^
foo.cpp:17:12: error: 'd' cannot be used as a function
 e=(2a-d(d+1))/2(d+1);
            ^
foo.cpp:17:20: error: expression cannot be used as a function
 e=(2a-d(d+1))/2(d+1);
                    ^
foo.cpp:18:8: error: 'd' cannot be used as a function
 f=d(d+1)(2*d+1)/6;
        ^
foo.cpp:6:17: warning: unused variable 'b' [-Wunused-variable]
 long long int a,b,c,e,f,g;
                 ^