#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, col1 = 0, col2 = 0, col3 = 0, col4 = 0, col5 = 0, col6 = 0;
  string s, s1, s2, s3, s4, s5, s6;
  cin >> n >> s;
  s1 = s, s2 = s, s3 = s, s4 = s, s5 = s, s6 = s;
  for (int i = 1; i <= 6; i++) {
    if (i == 1) {
      int pos = 1;
      for (int j = 0; j < s1.size(); j++) {
        if (pos == 1 && s1[j] != 'R') {
          s1[j] = 'R';
          col1++;
        } else if (pos == 2 && s1[j] != 'G') {
          s1[j] = 'G';
          col1++;
        } else if (pos == 3 && s1[j] != 'B') {
          s1[j] = 'B';
          col1++;
        }
        if (pos == 3) {
          pos = 1;
        } else {
          pos++;
        }
      }
    } else if (i == 2) {
      int pos = 1;
      for (int j = 0; j < s2.size(); j++) {
        if (pos == 1 && s2[j] != 'R') {
          s2[j] = 'R';
          col2++;
        } else if (pos == 2 && s2[j] != 'B') {
          s2[j] = 'B';
          col2++;
        } else if (pos == 3 && s2[j] != 'G') {
          s2[j] = 'G';
          col2++;
        }
        if (pos == 3) {
          pos = 1;
        } else {
          pos++;
        }
      }
    } else if (i == 3) {
      int pos = 1;
      for (int j = 0; j < s3.size(); j++) {
        if (pos == 1 && s3[j] != 'G') {
          s3[j] = 'G';
          col3++;
        } else if (pos == 2 && s3[j] != 'R') {
          s3[j] = 'R';
          col3++;
        } else if (pos == 3 && s3[j] != 'B') {
          s3[j] = 'B';
          col3++;
        }
        if (pos == 3) {
          pos = 1;
        } else {
          pos++;
        }
      }
    } else if (i == 4) {
      int pos = 1;
      for (int j = 0; j < s4.size(); j++) {
        if (pos == 1 && s4[j] != 'G') {
          s4[j] = 'G';
          col4++;
        } else if (pos == 2 && s4[j] != 'B') {
          s4[j] = 'B';
          col4++;
        } else if (pos == 3 && s4[j] != 'R') {
          s4[j] = 'R';
          col4++;
        }
        if (pos == 3) {
          pos = 1;
        } else {
          pos++;
        }
      }
    } else if (i == 5) {
      int pos = 1;
      for (int j = 0; j < s5.size(); j++) {
        if (pos == 1 && s5[j] != 'B') {
          s5[j] = 'B';
          col5++;
        } else if (pos == 2 && s5[j] != 'R') {
          s5[j] = 'R';
          col5++;
        } else if (pos == 3 && s5[j] != 'G') {
          s5[j] = 'G';
          col5++;
        }
        if (pos == 3) {
          pos = 1;
        } else {
          pos++;
        }
      }
    } else if (i == 6) {
      int pos = 1;
      for (int j = 0; j < s6.size(); j++) {
        if (pos == 1 && s6[j] != 'B') {
          s6[j] = 'B';
          col6++;
        } else if (pos == 2 && s6[j] != 'G') {
          s6[j] = 'G';
          col6++;
        } else if (pos == 3 && s6[j] != 'R') {
          s6[j] = 'R';
          col6++;
        }
        if (pos == 3) {
          pos = 1;
        } else {
          pos++;
        }
      }
    }
  }
  int min = col1;
  int b[5] = {col2, col3, col4, col5, col6};
  for (int i = 0; i < 5; i++) {
    if (b[i] < min) {
      min = b[i];
    }
  }
  if (min == col1) {
    cout << col1 << endl << s1;
    return 0;
  } else if (min == col2) {
    cout << col2 << endl << s2;
    return 0;
  } else if (min == col3) {
    cout << col3 << endl << s3;
    return 0;
  } else if (min == col4) {
    cout << col4 << endl << s4;
    return 0;
  } else if (min == col4) {
    cout << col4 << endl << s4;
    return 0;
  } else if (min == col4) {
    cout << col4 << endl << s4;
    return 0;
  } else if (min == col5) {
    cout << col5 << endl << s5;
    return 0;
  } else {
    cout << col6 << endl << s6;
    return 0;
  }
  return 0;
}
