#include <iostream>
using namespace std;
 
const int MAX_LENGTH = 30000;
 
int main() {
	int n, m, v[MAX_LENGTH + 1];
	cin >> n >> m;
	for (int i = 1; i <= n; ++i) {
		cin >> v[i] ;
		//cout << v[i] <<" ";
	}
	//cout << 5 / 2;
	int counter = 0;
	for (int i = 1, aux = 0; i <= n ; ++i, ++aux) {
		if (v[i] != v[n - aux]) {
			++counter;
		}
	}
 
 
	cout <<counter <<  "\n";
	int i = 1;
	int modifPos = 0, newVal = 0;
	while (i++ <= m){
		int newCounter = 0;
		cin >> modifPos >> newVal;
		for (int i = 1; i <= n; ++i) {
			if (i == modifPos) {
				v[i] = newVal;
			}
		}
		for (int i = 1, aux = 0; i <= n ; ++i, ++aux) {
			cout << v[i] << " " << v[n - aux] <<"\n";
			if (v[i] != v[n - aux]) {
				++newCounter;
			}
		}
		//cout << newCounter << "\n";
		//cout << modifPos <<  newVal << "\n";
	//	++i;
	cout << "\n";
	}
	return 0;
}

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NyA1CjEgMiAzIDQgNSA2IDcgCjIgMCAKMyAxIAo0IDAgCjcgMSAKNiAxIAo=

7 5
1 2 3 4 5 6 7 
2 0 
3 1 
4 0 
7 1 
6 1