View Compilation Error

0_0_33495323_11533.cpp:11:1: error: expected ';' before 'string'
 string a;
 ^
0_0_33495323_11533.cpp: In function 'int main()':
0_0_33495323_11533.cpp:18:10: error: 'sum' was not declared in this scope
   falg=1;sum=0;
          ^