/in/foo.cc: In function 'int main()':
/in/foo.cc:5:7: error: 'n' was not declared in this scope
  cin>>n;
       ^
/in/foo.cc:10:3: error: 'sum' was not declared in this scope
   sum+=fenzi/fenmu;
   ^~~
/in/foo.cc:15:8: error: 'sum' was not declared in this scope
  cout<<sum;
        ^~~
/in/foo.cc:4:8: warning: unused variable 'nsum' [-Wunused-variable]
  int i,nsum=0,fenzi,fenmu,t;
        ^~~~