View Compilation Error

0_0_26865583_8120.c: In function 'bbp':
0_0_26865583_8120.c:19:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for (int i=0;i<=n;i++) ans+=(double)qmod(16,n-i,8*i+k)/(8*i+k);
     ^
0_0_26865583_8120.c:19:5: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_26865583_8120.c:20:14: error: redefinition of 'i'
     for (int i=n+1;i<=n+1000;i++) ans+=pow(16,n-i)/(8*i+k);
              ^
0_0_26865583_8120.c:19:14: note: previous definition of 'i' was here
     for (int i=0;i<=n;i++) ans+=(double)qmod(16,n-i,8*i+k)/(8*i+k);
              ^
0_0_26865583_8120.c:20:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for (int i=n+1;i<=n+1000;i++) ans+=pow(16,n-i)/(8*i+k);
     ^
0_0_26865583_8120.c: In function 'main':
0_0_26865583_8120.c:37:1: error: expected expression before '/' token
 //        printf("%lf %d ",ans,anss);
 ^