#include <iostream>

using namespace std;
long long dp[100010][2],c[100010],d[100010];
int main(){
	int i,n;
	cin >> n;
	for(i=0;i<=n;i++){
		dp[i][0] = 100000000000000000;
		dp[i][1] = 100000000000000000;
	}
	dp[0][0] = 0;
	for(i=0;i<n;i++){
		cin >> c[i] >> d[i];
		dp[0][0] += c[i] + d[i];
	}
	dp[0][0] -= d[0]; dp[0][1] = dp[0][0] + c[0];
	for(i=1;i<n;i++){
		dp[i][0] = dp[i - 1][0];
		dp[i][1] = dp[i - 1][1];
		dp[i][0] = min(dp[i][0],dp[i - 1][1] - d[i]);
		dp[i][1] = min(dp[i][1],dp[i][0] + c[i]);
	}
	cout << dp[n - 1][1] << endl;
}