View Compilation Error

0_0_32938861_27981.c:4:1: error: unknown type name 'using'
 using namespace std;
 ^
0_0_32938861_27981.c:4:17: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'std'
 using namespace std;
                 ^
0_0_32938861_27981.c: In function 'main':
0_0_32938861_27981.c:11:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for(int i = 0; i < n; i++){
         ^
0_0_32938861_27981.c:11:9: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_32938861_27981.c:15:17: error: redefinition of 'i'
         for(int i = 1000000; i >= 0; i--){
                 ^
0_0_32938861_27981.c:11:17: note: previous definition of 'i' was here
         for(int i = 0; i < n; i++){
                 ^
0_0_32938861_27981.c:15:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for(int i = 1000000; i >= 0; i--){
         ^