UVA 1393 - Highways (容斥原理计数)

#include <stdio.h>
#include <string.h>

int n, m;
long long dp[305][305], ans[305][305];

int gcd(int a, int b) {
	if (b == 0) return a;
	return gcd(b, a % b);
}

int main() {
	for (int i = 1; i <= 300; i++)
		for (int j = 1; j <= 300; j++)
			dp[i][j] = dp[i - 1][j] + dp[i][j - 1] - dp[i - 1][j - 1] + (gcd(i, j) == 1);
	for (int i = 1; i <= 300; i++)
		for (int j = 1; j <= 300; j++)
			ans[i][j] = ans[i - 1][j] + ans[i][j - 1] - ans[i - 1][j - 1] + dp[i][j] - dp[i / 2][j / 2];
	while (~scanf("%d%d", &n, &m) && n || m) {
		printf("%lld\n", ans[n - 1][m - 1] * 2);
 	}
	return 0;
}