1 #include <iostream> 2 #include <string> 3 #include <sstream> 4 using namespace std; 5 string LongToString(long l) 6 { 7     stringstream str; 8     str<<l; 9     return str.str();10 }11 int main()12 {13     long l;14     cin>>l;15     string str = LongToString(l);16     size_t len = str.length();17     for(int index =(int) len-3; index > 0; index -= 3)18       str.insert(index, ",");19     cout<<str<<endl;20     return 0;21 }