問題：B - OddString #include <iostream> #include <string> using namespace std; int main(void) { string s, ans = ""; cin.tie(0); ios::sync_with_stdio(false); cin >> s; for (int i = 0; i < s.length(); i += 2) { ans += s[i]; } cout << ans << "\n"; return 0; }</string></iostream>