#include <iostream>
#include <fstream>


using namespace std;

#define maxN 1000
#define maxH 1000
int h[maxN];
int c[maxN];
int knownCosts[maxN];
int N = 0;
int globalMin = 0;

int solve(int start, int currentHeight);
int min(int, int);

int main(int argc, char** argv)
{
    ifstream in("input.txt");
    ofstream out("output.txt");
    in >> N;
    for(int i = 0; i < N ; i++)
    {
        in >> h[i];
        in >> c[i];
        knownCosts[i] = -1;
    }
    
    out << solve(0, maxH+1);
}


//lo prendo, non lo prendo
int solve(int start, int currentHeight)
{
	if(start >= N)
		return 0;	
	
	if(h[start] < currentHeight)
	{
		return min( 
			solve(start+1, h[start]),
			c[start] + solve(start+1, currentHeight)
			);
	}
	
	else
		return c[start] + solve(start+1, currentHeight);
}


int min(int a, int b)
{
	if(a < b)
		return a;
	
	return b;
}