문제

링크

풀이

#include <iostream>
#include <cmath>
using namespace std;
 
void solve(void) {
  int a, b; cin >> a >> b;
  int k, x; cin >> k >> x;
 
  int ans = 0;
  for (int i=a; i<=b; i++) {
    if (abs(k-i) <= x) ans++;
  }
  
  if (ans) cout << ans;
  else cout << "IMPOSSIBLE";
}
 
int main(void) {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
 
  solve();
  return 0;
}