View Compilation Error

0_0_33925268_30236.cpp: In function 'int main()':
0_0_33925268_30236.cpp:24:22: error: too many arguments to function 'long long int euler()'
   ans = (ans-(euler(n)*n/2)) % mod;
                      ^
0_0_33925268_30236.cpp:6:11: note: declared here
 long long euler(){
           ^