View Compilation Error

0_0_20687203_23366.c: In function 'read_input':
0_0_20687203_23366.c:10:2: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
  for(int i = 0; i < 6; i++) {
  ^
0_0_20687203_23366.c:10:2: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_20687203_23366.c: In function 'main':
0_0_20687203_23366.c:22:2: error: expected expression before '/' token
  // freopen("test.txt", "r", stdin);
  ^
0_0_20687203_23366.c:33:3: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
   for(int i = 0; i < 6; i++) {
   ^
0_0_20687203_23366.c:43:5: error: expected expression before '/' token
     // for(; j <= val; j++)
     ^
0_0_20687203_23366.c:47:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for(int j = 0; j <= val; j++) {
     ^
0_0_20687203_23366.c:72:2: error: expected expression before '/' token
  // fclose(stdin);
  ^