Răspuns :
#include <iostream>
#include <cstring>
#include <fstream>
using namespace std;
ifstream fin("text.in");
int main()
{
char sir[255];
int contor=0, i, len;
fin.getline(sir,255);
len=strlen(sir);
for (i=0; i<len; ++i)
{
if ((sir[i]>='A' && sir[i]<='Z') || (sir[i]>='a' && sir[i]<='z'))
{
++contor;
if (contor==3)
{
if (sir[i]>='a' && sir[i]<='z')
sir[i]=sir[i]-('a' -'A');
contor=0;
}
else
{
if (sir[i]>='A' && sir[i]<='Z')
sir[i]=sir[i]+('a'-'A');
}
}
}
cout <<sir;
return 0;
}
