#include <iostream>
#include <cstdio>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <map>
#include <math.h>
#include<iomanip>

using namespace std;

#define REP(i,n)	for(int i=0;i<(n);++i)
#define REPS(i,s,t)	for(int i=(s);i<(t);++i)

#define INF 		2000000007
#define MOD			998244353

#define MAX 		100005

typedef unsigned int 			uint;
typedef unsigned long long int	ull;
typedef long long int ll;


int main(){
	int n;cin>>n;

	int ans = 0;
	REP(i,n){
		int a,b;
		cin>>a>>b;
		ans += min(a,b);
	}
	cout << ans << endl;

	return 0;
}