#include <cstdio>
#define NN 201000
using namespace std;

int a[NN],b[NN],c[NN];
int n,ans;

int main(){
	freopen("boarding.in","r",stdin);
	freopen("boarding.out","w",stdout);
	int i,tem;
	scanf("%d",&n);
	for (i = 1; i <= n; i++){
		scanf("%d%d",&a[i],&b[i]);
		c[i] = 1;
		if (a[i] == n) tem = i;
	}
	a[0] = n+1;
	c[0] = 0;
	ans += 2*n-tem;
	for (i = n-1; i >= 0; i--){
		if (a[i] >  a[i+1])
			ans += b[i+1];
		else{
			if (b[i+1]-b[i] > (a[i+1]-a[i])*c[i]) ans += b[i+1]-b[i]-(a[i+1]-a[i])*c[i];
		}
	}
	printf("%d",ans);
	return 0;
}