View Compilation Error

0_0_29854082_15349.cpp: In function 'int main()':
0_0_29854082_15349.cpp:72:27: error: 'f' cannot be used as a function
    if(v[sl[idd]-1]>v[f(idd)]){
                           ^
0_0_29854082_15349.cpp:73:60: error: 'f' cannot be used as a function
     sp.push(DR{sl[idd]-1,d[sl[idd]-1]/(v[sl[idd]-1]-v[f(idd)])+q.nt});
                                                            ^