stringstream ssin(a)/ssin相当于cin/
#include <iostream>
#include <cstring>
#include <algorithm>
#include <sstream>
using namespace std;
int main()
{
string a,b,c;
getline(cin,a);
cin>>b>>c;
stringstream ssin(a);
string str;
while(ssin>>str)
if(str==b) cout<<c<<' ';
else cout<<str<<' ';
return 0;
}