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0_0_13110111_27297.cpp: In function 'double G(long long int, long long int)':
0_0_13110111_27297.cpp:6:80: error: expression cannot be used as a function
 double G(ll j,ll k) {return (double)(f[j]+s[j]*s[j]-f[k]-s[k]*s[k])/2(s[j]-s[k]);}
                                                                                ^