View Compilation Error

0_0_18212965_2052.c: In function 'main':
0_0_18212965_2052.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_18212965_2052.c:11:3: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_18212965_2052.c:17:12: error: redefinition of 'i'
   for (int i = n; i >= 1; i--)
            ^
0_0_18212965_2052.c:11:12: note: previous definition of 'i' was here
   for (int i = 1; i <= n; i++)
            ^
0_0_18212965_2052.c:17:3: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
   for (int i = n; i >= 1; i--)
   ^