View Compilation Error

0_0_37141396_30548.cpp:8:3: error: missing terminating " character
   printf("%lld\n\n%lld,a,sum);
   ^
0_0_37141396_30548.cpp: In function 'int main()':
0_0_37141396_30548.cpp:7:8: error: 'n' was not declared in this scope
    sum=n*(n+1)/2;
        ^
0_0_37141396_30548.cpp:9:5: error: expected primary-expression before 'return'
     return 0;
     ^