View Compilation Error

0_0_19842058_9221.c: In function 'main':
0_0_19842058_9221.c:6:3: error: expected expression before '/' token
   //fflush(stdin); 
   ^
0_0_19842058_9221.c:11:3: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
   for (int i=1;i<n;i++){
   ^
0_0_19842058_9221.c:11:3: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code