foo.c: In function 'main':
foo.c:13:5: error: 'for' loop initial declarations are only allowed in C99 mode
     for(int i=0;i<n;i++)
     ^
foo.c:13:5: note: use option -std=c99 or -std=gnu99 to compile your code
foo.c: In function 'D':
foo.c:64:5: error: 'for' loop initial declarations are only allowed in C99 mode
     for(int i=0;i<30;i++)
     ^
foo.c: In function 'main':
foo.c:33:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^