View Compilation Error

0_0_29068289_23549.cpp: In function 'int main()':
0_0_29068289_23549.cpp:15:27: error: expected primary-expression before 'long'
             a = to_string(long long (sum));
                           ^
0_0_29068289_23549.cpp:20:12: error: expected 'while' before numeric constant
     return 0;
            ^
0_0_29068289_23549.cpp:20:12: error: expected '(' before numeric constant
0_0_29068289_23549.cpp:20:13: error: expected ')' before ';' token
     return 0;
             ^
0_0_29068289_23549.cpp:21:1: error: expected '}' at end of input
 }
 ^