Untitled

#include <iostream>
#include <vector>

int main() {
	int n = 0;
	int m = 0;
	char tmp = '.';
	std::vector<std::vector<char>> v;
	std::cin >> n >> m;

	for (int i = 0; i < n; i++) {
		v.push_back({});
		for (int j = 0; j < m; j++) {
			if ((i + j) % 2 == 1) {
				tmp = '*';
			}
			v[i].push_back(tmp);
			tmp = '.';
		}
	}

	for (int i = 0; i < n; i++) {
		for (int j = 0; j < m; j++) {
			std::cout << v[i][j] << ' ';
		}
		std::cout << '\n';
	}
}