include[HTML_REMOVED]

using namespace std;

define endl “\n”

define ll long long

define ull unsigned long long

define int long long

define fi first

define se second

define all(x) x.begin(), x.end()

define rall(x) x.rbegin(), x.rend()

typedef pair[HTML_REMOVED] PII;
// queue[HTML_REMOVED] q;

const int N = 2e5 + 10, mod = 998244353, p = 1e9 + 7;

int exgcd(int a, int b, int &x, int &y) {
if(!b) {
x = 1, y = 0;
return a;
}

int d = exgcd(b, a % b, y, x);
y -= a / b * x;

return d;

}

void solve(){
int n;
cin >> n;

int M = 1;
vector<int> a(n), b(n);
for(int i = 0; i < n; i++) {
    cin >> a[i] >> b[i];
    M *= a[i];
}

int x, y, ans = 0;
for(int i = 0; i < n; i++) {
    int mi = M / a[i];
    int d = exgcd(mi, a[i], x, y);
    ans = (ans + b[i] * x * mi) % M;
}

cout << (ans % M + M) % M << endl;

}

signed main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);

int t = 1;
// cin >> t;

while(t--) {
    solve();
}

return 0;

}