View Compilation Error

0_0_30058474_31910.cpp: In function 'int main()':
0_0_30058474_31910.cpp:19:23: error: 'f' cannot be used as a function
    f[n] = (a * f(n - 1) + b * f(n - 2)) % 7;
                       ^
0_0_30058474_31910.cpp:19:38: error: 'f' cannot be used as a function
    f[n] = (a * f(n - 1) + b * f(n - 2)) % 7;
                                      ^