View Compilation Error

0_0_25171154_13648.c: In function 'main':
0_0_25171154_13648.c:6:6: error: conflicting types for 'a'
  int a[50];
      ^
0_0_25171154_13648.c:5:6: note: previous declaration of 'a' was here
  int a, b, n;
      ^
0_0_25171154_13648.c:22:4: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
    for(int i = 3; i<=n; i++)
    ^
0_0_25171154_13648.c:22:4: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_25171154_13648.c:24:15: error: invalid operands to binary * (have 'int *' and 'int')
     a[i] = ((a*a[i-1]) + (b*a[i-2]));
               ^
0_0_25171154_13648.c:27:17: error: 'f' undeclared (first use in this function)
    printf("%d", f[n]);
                 ^
0_0_25171154_13648.c:27:17: note: each undeclared identifier is reported only once for each function it appears in