View Compilation Error

0_0_30903267_20411.c: In function 'main':
0_0_30903267_20411.c:8:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for (int i = 0; i < n; i++) {
         ^
0_0_30903267_20411.c:8:9: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_30903267_20411.c:12:13: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
             for (int j = 0; j < len / 2; j++) {
             ^
0_0_30903267_20411.c:18:5: error: expected declaration or statement at end of input
     return 0;
     ^