#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, cntx = 0, cntX = 0, c = 0;
  cin >> n;
  string s;
  cin >> s;
  for (int i = 0; i < n; i++) {
    if (s[i] == 'x')
      cntx++;
    else
      cntX++;
  }
  int i = 0;
  if (cntx > cntX) {
    while (cntx != cntX) {
      if (s[i] == 'x') {
        s[i] = 'X';
        cntx--;
        c++;
        cntX++;
      }
      i++;
    }
  } else {
    while (cntx != cntX) {
      if (s[i] == 'X') {
        s[i] = 'x';
        cntX--;
        cntx++;
        c++;
      }
      i++;
    }
  }
  cout << c << endl << s << endl;
  return 0;
}
