View Compilation Error

0_0_16915098_4995.cpp:7:1: error: 'll' does not name a type
 ll mod_mul(ll x,ll y,ll n) {
 ^
0_0_16915098_4995.cpp: In function 'int main()':
0_0_16915098_4995.cpp:23:53: error: 'mod_mul' was not declared in this scope
    printf("%I64d\n", mod_mul((q - 2), (q - 1) / 2, p));
                                                     ^