View Compilation Error

0_0_15837858_9850.cpp: In function 'int main()':
0_0_15837858_9850.cpp:10:34: error: 'n' was not declared in this scope
      for(int i=2;(long long)i*i<=n;i++){
                                  ^
0_0_15837858_9850.cpp:16:9: error: 'n' was not declared in this scope
      if(n>1) res=res/n*(n-1);
         ^