#include <iostream>
#include <vector>
int main () {
std::vector<int> vec {1, 2, 3, 4, 5, 6, 7, 8, 9};
auto it = vec.begin();
vec.insert(it + 3, 10);
for (auto x: vec) std::cout << ' ' << x;
}
//https://pt.stackoverflow.com/q/110841/101
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