#include <iostream>

int keyvalue(char c)
{
	return std::tolower(c) - 'a';
}
int main(int argc, char** argv)
{
	char* text;
	char* key;
	if(argc < 3)
	{
		std::cout << "Usage: " << argv[0] << " <plain text> <key>" << std::endl;
		return 0;
	}

	text = argv[1];
	key = argv[2];

	int ki = 0;
	for(int pi = 0; text[pi] != 0; ++pi)
	{
		if(text[pi] == ' ')
		{
			std::cout << ' ';
			continue;
		}
		// has to be int, because the result can sometimes be > 127
		int c = std::tolower(text[pi]) + keyvalue(key[ki]);
		if(c < 'a') c+=26;
		if(c > 'z') c-=26;
		std::cout << (char)c;
		if(key[++ki] == 0) ki = 0;
	}
	std::cout << std::endl;
	return 0;
}