What is the problem with this code?

Question

vector<int> permutationEquation(vector<int> p) {

vector<int> s;

for(int i=0;i<p.size();i++)
{
vector<int>::iterator it = find(p.begin(),p.end(),i);
int z = p.at(it);
s[i]= find(p.begin(),p.end(),z);
}

return s;
}

error : "no instance of overloaded function \"std::vector<_Ty, _Alloc>::at [with _Ty=int, _Alloc=std::allocator<int>]\" matches the argument list -- argument types are: (std::_Vector_iterator<std::_Vector_val<std::conditional_t<true, std::_Simple_types<int>, std::_Vec_iter_types<int, size_t, ptrdiff_t, int *, const int *, int &, const int &>>>>) -- object type is: std::vector<int, std::allocator<int>>",
"startLineNumber": 15,

error 2 : "no suitable conversion function from
\"std::_Vector_iterator<std::_Vector_val<std::conditional_t<true,
std::_Simple_types<int>, std::_Vec_iter_types<int, size_t, ptrdiff_t, int *, const
int *, int &, const int &>>>>\" to \"int\" exists",
"startLineNumber": 16,
"startColumn": 10,
"endLineNumber": 16,
"endColumn": 14
}
"startColumn": 15,
"endLineNumber": 15,
"endColumn": 17
}