//
// Problem: Elevator Hall Number
// Solution by: MORI Shingo
// DFA Answer
//
// implement 26min
// debug 9min
// 
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <iostream>
#include <math.h>
#include <assert.h>
#include <vector>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <numeric>

using namespace std;
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
static const long double EPS = 1e-9;
static const long double PI = acos(-1.0);

#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define FOR(i, s, n) for (int i = (s); i < (int)(n); i++)
#define FOREQ(i, s, n) for (int i = (s); i <= (int)(n); i++)
#define FORIT(it, c) for (__typeof((c).begin())it = (c).begin(); it != (c).end(); it++)
#define MEMSET(v, h) memset((v), h, sizeof(v))

map<set<int>, ll> memo;
int n;
int ls[10];
int rs[10];

ll calc(const set<int> &state) {
  if (state.empty()) { return 0; }
  if (memo.count(state)) { return memo[state]; }
  ll &ret = memo[state] = 0;
  if (*state.rbegin() == n * 8) { ret++; }
  FOREQ(v, 0, 9) {
    set<int> nstate;
    FORIT(it, state) {
      if (*it == n * 8) { continue; }
      int i = *it / 8;
      int s = *it % 8;
      assert(0 <= i && i < n);
      assert(0 <= s && s < 8);
      if (s == 0) {
        if (v != 0 && ls[i] / 10 <= v && v <= rs[i] / 10) {
          int ns = 1;
          if (ls[i] / 10 == v) { ns |= 2; }
          if (rs[i] / 10 == v) { ns |= 4; }
          nstate.insert(i * 8 + ns);
        }
        if (ls[i] <= v && v <= rs[i]) {
          nstate.insert((i + 1) * 8);
        }
      } else {
        int ni = i + 1;
        if ((s & 2) && v < ls[i] % 10) { continue; }
        if ((s & 4) && rs[i] % 10 < v) { continue; }
        nstate.insert(ni * 8);
      }
    }
    ret += calc(nstate);
  }
  return ret;
}

int main() {
  while (scanf("%d", &n) > 0 && n) {
    memo.clear();
    REP(i, n) {
      int v = scanf("%d %d", &ls[i], &rs[i]);
      assert(v == 2);
    }
    set<int> state;
    state.insert(0);
    ll ans = calc(state);
    printf("%lld\n", ans);
  }
}