#include <stdio.h>
#include <conio.h>
#include <string.h>

#define MESSAGE_MAX_LENGHT 100;

int encrypt(int value,int key);
int decrypt(int value,int key);
void encryptMessage(char* input, int key);
void decryptMessage(char* input, int key);

int main(){
	int key;
	char input[MESSAGE_MAX_LENGHT];

	printf("Introdu mesajul: ");
	gets(input);

	printf("Indou cheia:");
	scanf("%d",&key);

	encryptMessage(input, key);
	printf("Mesajul criptat: %s\n", input);

	decryptMessage(input, key);
	printf("Mesajul decriptat: %s\n", input);


}

int encrypt(int value, int key){
	int result=(value+key)%26;
	return result;
}

int decrypt(int value, int key){
	int result=(value-key+26)%26;
	return result;
}

void encryptMessage(char * input, int key){
	char message[MESSAGE_MAX_LENGHT];
	strcpy(message,input);

	int index=0;
	while(message[index] != '\0'){
		if(message[index] != ' ')
			if(message[index] <= 'Z' && message[index] >='A')
				input[index]=encrypt(message[index] - 'A' ,key) + 'A';
			else input[index]=encrypt(message[index] - 'a', key) + 'a';
		index++;
	}
}

void decryptMessage(char * input, int key){
	char message[MESSAGE_MAX_LENGHT];
	strcpy(message,input);
	int index=0;
	while(message[index] != '\0'){
		if(message[index] != ' ')
			if(message[index] <= 'Z')
				input[index] = decrypt(message[index] - 'A', key)+'A';
			else input[index] =decrypt(message[index] - 'a', key)+'a';

	}
}