Планета роботов — школьный этап 2016

#include <fstream>
#include <string>
using namespace std;
string convertToBinary(int y) {
	string a;
	while (y > 0) {
		if (y % 2 == 0)
			a += "0";
		else
			a += "1";
		y /= 2;
	}
	return a;
}
int main()
{
	ifstream fin("input.txt");
	ofstream fout("output.txt");
	string s, b;
	int i, k=1, x=0;
	fin >> s;
	i = s.length() - 1;
	while (i >= 0) {
		if (s[i] >= '0' && s[i] <= '9') {
			x += (s[i] - '0')*k;
			k *= 10;
		}else if (s[i+1] >= '0' && s[i+1] <= '9') {
			b += convertToBinary(x);
			b += s[i];
			x = 0;
			k = 1;
		}
		else {
			b += s[i];
		}
		i--;
	}
	if (x != 0)
		b += convertToBinary(x);
	for (int j = b.length() - 1;j >= 0;j--)
		fout << b[j];
	return 0;
}