include<bits/stdc++.h>
using namespace std;
#define int long long
int a[100001], b[100001];
int ans;
int t;
int flag[10001];
int g;
signed main() {
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> a[i] >> b[i];
		t++;
		g++;
		if (b[i] == 1) {
			t--;
//			flag[++g] = a[i];
			ans += (a[i]) + (t) * 20;
			t = 0;
		}
		if (i == n && ans == 0) {
			ans += a[i] + (n - 1) * 20;
		}
	}
	cout << ans;
	return 0;
}
/*
5
1 0
2 0
3 0
35 1
91 0
*/

why?