#include <cstdio>
int n, a, b, l = 200000, c[400009]; long long ret;
int main() {
	scanf("%d", &n);
	while (n--) {
		scanf("%d %d", &a, &b);
		ret += c[b - a + l];
		c[a - b + l]++;
	}
	printf("%lld\n", ret);
}