src.cpp:6:19: error: array bound is not an integer constant before ']' token
long long int a[i];
^
src.cpp: In function 'int main()':
src.cpp:15:32: error: 'a' was not declared in this scope
for( int i=1;i<=n;i++)cin>>a[i];
^
src.cpp:16:17: error: 'a' was not declared in this scope
min_element(a-1 ,a+1+n);
^