#include<iostream> #include<string> #include<cstdio> #include<vector> #include<cmath> #include<algorithm> #include<functional> #include<iomanip> #include<queue> #include<ciso646> #include<random> #include<map> #include<set> #include<complex> #include<bitset> #include<stack> #include<unordered_map> #include<utility> using namespace std; typedef long long ll; typedef unsigned int ui; const ll mod = 1000000007; typedef long double ld; const ll INF = mod * mod; typedef pair<int, int> P; #define stop char nyaa;cin>>nyaa; #define rep(i,n) for(int i=0;i<n;i++) #define per(i,n) for(int i=n-1;i>=0;i--) #define Rep(i,sta,n) for(int i=sta;i<n;i++) #define rep1(i,n) for(int i=1;i<=n;i++) #define per1(i,n) for(int i=n;i>=1;i--) #define Rep1(i,sta,n) for(int i=sta;i<=n;i++) typedef complex<ld> Point; const ld eps = 1e-8; const ld pi = acos(-1.0); typedef pair<ld, ld> LDP; typedef pair<ll, ll> LP; int n; LP x[2000]; ll dp[2001][2001]; int main() { cin >> n; rep(i, n) { cin >> x[i].second >> x[i].first; } sort(x, x + n,greater<LP>()); rep(i, n+1) { rep(j, n + 1) { dp[i][j] = INF; } } dp[0][0] = 0; int m = n; int cop = n; while (cop > 0) { cop--; if (cop >= 2) { m--; } cop -= 2; } rep(i, n) { rep(j, i + 1) { //買う dp[i + 1][j + 1] = min(dp[i + 1][j + 1], dp[i][j] + x[i].second + j * x[i].first); //買わない dp[i + 1][j] = min(dp[i + 1][j], dp[i][j]); } } cout << dp[n][m] << endl; //stop return 0; }