#include<bits/stdc++.h>
#include<bits/extc++.h>
#define int long long
#define inf 0x3f3f3f3f3f3f3f3f
#define maxn 2234
#define eps 1e-7
#define mod 1000000007
#define Mod 998244353
#define f(i,a,b) for(int i=a;i<=b;i++)
#define r(i,a,b) for(int i=a;i>=b;i--) 
#define fx(i,a,b,x) for(int i=a;i<=b;i+=x)
#define rx(i,a,b,x) for(int i=a;i>=b;i-=x) 
using namespace std;
using namespace __gnu_cxx;
using namespace __gnu_pbds;
int T;
int n,dp[maxn][maxn];
struct node{
	int a,b;
}x[maxn];
bool operator<(const node&x,const node&y){
	return x.b>y.b;
}
int Min(int a,int b){
	return a<b?a:b;
}
int Max(int a,int b){
	return a>b?a:b;
}
void solve(){
	scanf("%lld",&n);
	f(i,0,n-1)scanf("%lld%lld",&x[i].a,&x[i].b);
	sort(x,x+n);
	f(i,0,n)
		f(j,0,n)dp[i][j]=inf;
	dp[0][0]=0;
	f(i,0,n-1){
		f(j,0,n/3){
			dp[i+1][j+1]=Min(dp[i+1][j+1],dp[i][j]);
			dp[i+1][j]=Min(dp[i+1][j],dp[i][j]+x[i].a+x[i].b*(i-j));
		}
	}
	printf("%lld\n",dp[n][n/3]);
}
signed main(){
	T=1;
//	scanf("%lld",&T);
	while(T--)solve();
	return 0;
}
/*
TIME: 2026-04-22 21:30:52
PROBLEM: XMOJ P11388
AUTHOR: 2333_qwq Luogu uid 951212
*/