#include <bits/stdc++.h>
using namespace std;
int dp[1000000][3];
int pre[1000500][3];
char a[1000500];
char ans[1000500];
void init() {
  for (int i = 0; i < 1000000; i++) {
    for (int j = 0; j < 3; j++) {
      pre[i][j] = -1;
    }
  }
  for (int i = 0; i < 1000000; i++) {
    for (int j = 0; j < 3; j++) {
      dp[i][j] = 0x3f3f3f3f;
    }
  }
}
int main() {
  while (~scanf("%s", a)) {
    int n = strlen(a);
    if (n == 1) {
      if ((a[0] - '0') % 3 == 0)
        printf("%c\n", a[0]);
      else
        printf("-1\n");
      continue;
    }
    init();
    dp[0][0] = 1;
    dp[0][(a[0] - '0') % 3] = 0;
    for (int i = 1; i < n; i++) {
      for (int j = 0; j < 3; j++) {
        if (dp[i - 1][j] + 1 < dp[i][j])
          dp[i][j] = dp[i - 1][j] + 1, pre[i][j] = j;
        if ((a[i] - '0') % 3 == 0) {
          if (a[i] == '0') {
            if (dp[i - 1][j] != i) {
              if (dp[i - 1][j] < dp[i][j]) {
                dp[i][j] = dp[i - 1][j];
                pre[i][j] = j;
              }
            }
          } else {
            if (dp[i - 1][j] < dp[i][j]) {
              dp[i][j] = dp[i - 1][j];
              pre[i][j] = j;
            }
          }
        }
        if ((a[i] - '0') % 3 == 1) {
          if (dp[i - 1][((j - 1) % 3 + 3) % 3] < dp[i][j]) {
            dp[i][j] = dp[i - 1][((j - 1) % 3 + 3) % 3];
            pre[i][j] = ((j - 1) % 3 + 3) % 3;
          }
        }
        if ((a[i] - '0') % 3 == 2) {
          if (dp[i - 1][((j - 2) % 3 + 3) % 3] < dp[i][j]) {
            dp[i][j] = dp[i - 1][((j - 2) % 3 + 3) % 3];
            pre[i][j] = ((j - 2) % 3 + 3) % 3;
          }
        }
      }
    }
    if (dp[n - 1][0] == n) {
      int flag = 0;
      for (int i = 0; i < n; i++) {
        if (a[i] == '0') flag = 1;
      }
      if (flag == 1)
        printf("0\n");
      else
        printf("-1\n");
      continue;
    }
    int cnt = 0;
    int now = n - 1;
    int j = 0;
    while (now >= 1) {
      int pree = pre[now][j];
      if (dp[now - 1][pree] == dp[now][j]) {
        ans[cnt++] = a[now];
      }
      j = pree;
      now--;
      if (now == 0) {
        if (pree == (a[0] - '0') % 3) {
          ans[cnt++] = a[now];
        }
      }
    }
    for (int i = cnt - 1; i >= 0; i--) {
      printf("%c", ans[i]);
    }
    printf("\n");
  }
}
