#include <iostream>
using namespace std;
#include <vector>
int main(){
std::vector<int> a = {1, 2, 3, 4};
for(auto i = a.begin(); i != a.end(); )
if(*i == 3)
i = a.erase(i);
else
i++;
for(auto &i: a)
cout << i << " ";
}