#include <bits/stdc++.h>
using namespace std;
int n, arr[100005], diff[100005], prv[100005];
bool flag[100005];
vector<int> a, d;
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) {
    scanf("%d", arr + i);
    flag[arr[i]] = 1;
  }
  for (int i = 1; i <= n; ++i) {
    if (!flag[arr[i]]) continue;
    if (prv[arr[i]] && !diff[arr[i]])
      diff[arr[i]] = i - prv[arr[i]];
    else if (prv[arr[i]] && diff[arr[i]] != i - prv[arr[i]])
      flag[arr[i]] = 0;
    prv[arr[i]] = i;
  }
  for (int i = 0; i < 100005; ++i)
    if (flag[i]) a.push_back(i), d.push_back(diff[i]);
  printf("%d\n", a.size());
  for (int i = 0; i < a.size(); ++i) printf("%d %d\n", a[i], d[i]);
  return 0;
}
