#include <stdio.h>
#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000000000000



int main(){
	
	int N;
	cin>>N;
	
	vector<pair<long long,long long>> X(N);

	rep(i,N){
		cin>>X[i].second>>X[i].first;
	}
	
	sort(X.rbegin(),X.rend());
	
	int D = 0;
	int n = N;
	
	rep(i,10000){
		n--;
		if(i%2 && n!=0){
			n--;
			D++;
		}
		if(n==0)break;
	}
	
	vector<long long> dp(D+1,Inf);
	dp[0] = 0;
	
	rep(i,N){
		vector<long long> ndp(D+1,Inf);
		
		rep(j,D+1){
			if(dp[j]==Inf)continue;
			if(j!=D){
				ndp[j+1] = min(ndp[j+1],dp[j]);
			}
			ndp[j] = min(ndp[j],dp[j] + X[i].second + X[i].first * (i-j));
		}
		swap(dp,ndp);
	}
	
	cout<<dp.back()<<endl;
	
    return 0;
}