#include <vector>
#include <iostream>
 
template<class T>
class matrix {
public:
  matrix(size_t width, size_t height) : data_(width, std::vector<T>(height, T())) {}
 
  T& at(size_t x, size_t y) {
    return data_.at(x).at(y);
  }
 
  const T& at(size_t x, size_t y) const {
    return data_.at(x).at(y);
  }
 
private:
  std::vector<std::vector<T>> data_;
};
 
int main() {
  int w = 20;
  int h = 30;
  matrix<int> foo(w, h);
  foo.at(0, 0) = 1;
  foo.at(1, 2) = 2;
  std::cout << foo.at(1, 2);
}

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