#include<bits/stdc++.h>
using namespace std;
#define int long long
struct St {
int d, x, end;
};
int n;
vector<St> stations;
vector<int> tt;
const int MOD = 1e9 + 7;
int ans = 0;
#define DEBUG false
// returns the number of diff routes starting at src.
int dp(int src, bool force_stop) {
if (DEBUG) cout << "dp:" << src << ", " << force_stop << endl;
// simple case: if force_stop just return 1
if (force_stop) {
return 1;
}
if (tt[src] != -1) return tt[src];
auto& st = stations[src]; int d = st.d, end = st.end;
if (DEBUG) cout << d << " " << end << endl;
// simple case: if d == 0 then we must stop also
if (d == 0) {
return 1;
}
// we can either stop here (ans++)
// or we can take the train (to src + d, src + ..., <= end)
// note that at some dest station e, we MUST STOP at e (i.e. cannot get on)
// if the train there has the same d AND ends before us
// this is to prevent double counting of the stations after e
// otherwise, if it ends after us, then we give the choice not to stop at e
// and instead can take a new train starting there
// however, this current dp function must then stop at e, allowing e to count
// the rest of the stations
int value = 0;
// easier case: stop here
value += 1;
if (!force_stop) {
int e = src + d;
while (e <= end) {
if (DEBUG) cout << src << " wl: " << e << " <= " << end << endl;
auto& st2 = stations[e]; int d2 = st2.d, end2 = st2.end;
if (d2 != d) {
// easier case
value += dp(e, false);
if (DEBUG) {
cout << "case1 " << src << "->" << e << " , newV=" << value << endl;
}
}
else {
if (end2 <= end) {
// force stop
//value += dp(e, true);
value += dp(e, false);
if (DEBUG) {
cout << "case2.1 " << src << "->" << e << endl;
}
}
else {
// we don't force stop, but immediately terminate while loop
value += dp(e, false);
if (DEBUG) {
cout << "case2.2 " << src << "->" << e << endl;
}
//break;
}
}
e += d;
}
}
value %= MOD;
tt[src] = value;
if (DEBUG) cout << "dp:" << src << ", " << force_stop << " = " << value << endl;
return value;
}
signed main() {
cin >> n;
stations.resize(n+1);
tt.resize(n+1, -1);
for (int i = 1; i <= n; i++) {
int d, x; cin >> d >> x;
long long end = min((long long)n, (long long)i + d * x);
stations[i] = {d, x, (int)end};
}
ans = dp(1, false);
cout << ans << endl;
}
