src.cpp:3:17: error: 'n' was not declared in this scope
long long int a[n];
^
src.cpp: In function 'int main()':
src.cpp:11:28: error: 'a' was not declared in this scope
for(i=1;i<=n;i++) cin>>a[i];
^
src.cpp:12:10: error: 'a' was not declared in this scope
sort(a+1,a+1+n);
^