View Compilation Error

0_0_15108640_17872.c: In function 'main':
0_0_15108640_17872.c:23:14: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
              for(int i=count_of1(D);i<S1;i++)
              ^
0_0_15108640_17872.c:23:14: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code