// string::rfind
#include <iostream>
#include <string>
using namespace std;
int main ()
{
string str ("The sixths sick sheik's sixths sixths sheep's sick.");
string key ("sixths");
size_t found;
found=str.rfind(key);
if (found!=string::npos)
str.replace (found,key.length(),"seventh");
cout << str << endl;
return 0;
}
Ly8gc3RyaW5nOjpyZmluZAojaW5jbHVkZSA8aW9zdHJlYW0+CiNpbmNsdWRlIDxzdHJpbmc+CnVzaW5nIG5hbWVzcGFjZSBzdGQ7CgppbnQgbWFpbiAoKQp7CiAgc3RyaW5nIHN0ciAoIlRoZSBzaXh0aHMgc2ljayBzaGVpaydzIHNpeHRocyBzaXh0aHMgc2hlZXAncyBzaWNrLiIpOwogIHN0cmluZyBrZXkgKCJzaXh0aHMiKTsKICBzaXplX3QgZm91bmQ7CgogIGZvdW5kPXN0ci5yZmluZChrZXkpOwogIGlmIChmb3VuZCE9c3RyaW5nOjpucG9zKQogICAgc3RyLnJlcGxhY2UgKGZvdW5kLGtleS5sZW5ndGgoKSwic2V2ZW50aCIpOwoKICBjb3V0IDw8IHN0ciA8PCBlbmRsOwoKICByZXR1cm4gMDsKfQ==