View Compilation Error

0_0_34363295_9495.cpp: In function 'void change(long long unsigned int, long long unsigned int)':
0_0_34363295_9495.cpp:27:3: error: 'ans' was not declared in this scope
   ans-=(totaln-nn[fu]-nn[fv])*nn[fu]*nn[fv]%mod;
   ^