View Compilation Error

0_0_26474281_11283.c: In function 'zhishu':
0_0_26474281_11283.c:22:2: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
  for(int i=2;i*i<maxn;i++)
  ^
0_0_26474281_11283.c:22:2: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_26474281_11283.c:26:4: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
    for(int j=i*i;j<maxn;j+=i)
    ^
0_0_26474281_11283.c:31:10: error: redefinition of 'i'
  for(int i=2;i<maxn;i++)
          ^
0_0_26474281_11283.c:22:10: note: previous definition of 'i' was here
  for(int i=2;i*i<maxn;i++)
          ^
0_0_26474281_11283.c:31:2: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
  for(int i=2;i<maxn;i++)
  ^
0_0_26474281_11283.c: In function 'main':
0_0_26474281_11283.c:65:3: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
   for(int i=0;i<=780;i++)
   ^