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#include<cstdlib>
#include<cstdio>
#include<cstring>
#include<cstdint>
#include "message.h"
#include "teatr.h"

const int MAX_SINGLE = 1000;
int NODES, MY_ID, N, PARTS, PART_LENGTH, MY_P1, MY_P2, MY_P1_LENGTH;
int* MY_SORTED_P1;
int* TMP_BUF;

int64_t mergesort(int* a, int N) {
	int rght, wid, rend, i, j, m, t;
	int64_t swaps = 0;
	for (int k = 1; k < N; k <<= 1) {
		for (int left = 0; left + k < N; left += k << 1) {
			rght = left + k;
			rend = rght + k;
			if (rend > N) {
				rend = N;
			}
			m = left;
			i = left;
			j = rght;
			while (i < rght && j < rend) {
				if (a[i] <= a[j]) {
					TMP_BUF[m] = a[i];
					++i;
				} else {
					TMP_BUF[m] = a[j];
					++j;
					swaps += rght - i;
				}
				++m;
			}
			while (i < rght) {
				TMP_BUF[m] = a[i];
				++i;
				++m;
			}
			while (j < rend) {
				TMP_BUF[m] = a[j];
				++j;
				++m;
			}
			if (rend - left >= 8) {
				std::memcpy(a + left, TMP_BUF + left, (rend - left) * sizeof(int));
			}
			else {
				for (m = left; m < rend; ++m) {
					a[m] = TMP_BUF[m];
				}
			}
		}
	}
	return swaps;
}

int64_t sort_my_p1() {
	int start = PART_LENGTH * MY_P1;
	int end = start + PART_LENGTH;
	if (end > N) {
		end = N;
	}
	MY_P1_LENGTH = end - start;
	MY_SORTED_P1 = (int*)malloc((MY_P1_LENGTH + 8) * sizeof(int));
	for (int i = start; i < end; ++i) {
		MY_SORTED_P1[i - start] = GetElement(i);
	}
	return mergesort(MY_SORTED_P1, MY_P1_LENGTH);
}

int64_t load_my_p2() {
	int start = PART_LENGTH * MY_P2;
	int end = start + PART_LENGTH;
	if (end > N) {
		end = N;
	}
	int len = end - start;
	int* sorted_p2 = (int*)malloc((len + 8) * sizeof(int));
	for (int i = start; i < end; ++i) {
		sorted_p2[i - start] = GetElement(i);
	}
	mergesort(sorted_p2, len);
	int i = 0;
	int j = 0;
	int64_t res = 0;
	while (i < len && j < MY_P1_LENGTH) {
		if (sorted_p2[i] <= MY_SORTED_P1[j]) {
			++i;
		} else {
			++j;
			res += len - i;
		}
	}
	return res;
}

void single() {
	int* heights = (int*)malloc((N + 8) * sizeof(int));
	int ret = 0;
	for (int i = 0; i < N; ++i) {
		heights[i] = GetElement(i);
		for (int j = 0; j < i; ++j) {
			if (heights[j] > heights[i]) {
				++ret;
			}
		}
	}
	printf("%lld\n", ret);
}

int main() {
	NODES = NumberOfNodes();
	MY_ID = MyNodeId();
	N = GetN();
	if (N <= MAX_SINGLE) {
		if (MY_ID == 0) {
			single();
		}
		return 0;
	}
	PARTS = 0;
	while (2 + PARTS * (PARTS - 1) <= 2 * NODES) {
		++PARTS;
	}
	--PARTS;
	PART_LENGTH = N % PARTS ? (N + PARTS) / PARTS : N / PARTS;
	if (2 + PARTS * (PARTS - 1) <= 2 * MY_ID) {
		MY_P1 = -1;
		MY_P2 = -1;
	}
	else if (MY_ID == 0) {
		MY_P1 = 0;
		MY_P2 = -1;
	}
	else {
		MY_P1 = 0;
		MY_P2 = 0;
		for (int i = 0; i < MY_ID; ++i) {
			if (MY_P2 == 0) {
				++MY_P1;
				MY_P2 = MY_P1 - 1;
			}
			else {
				--MY_P2;
			}
		}
	}
	int64_t res = 0;
	if (MY_P1 >= 0) {
		TMP_BUF = (int*)malloc((PART_LENGTH + 8) * sizeof(int));
		int64_t internal = sort_my_p1();
		if (MY_P2 <= 0) {
			res = internal;
		}
	}
	if (MY_P2 >= 0) {
		res += load_my_p2();
	}
	if (MY_ID > 0) {
		PutLL(0, res);
		Send(0);
		return 0;
	}
	for (int i = 1; i < NODES; ++i) {
		Receive(i);
		res += GetLL(i);
	}
	printf("%lld\n", res);
	return 0;
}