# include<bits/stdc++.h>
using namespace std;
const int N=10e5+5;
int arr[N];
int main() {
	int m, n, total = 0;
	cin>> m >> n;
	for(int i = 0; i < n; i++) {
		int k, p;
		cin>> k >> p;
		if(arr[k] == 0) {
			arr[k] = p;
		} else {
			arr[k] = min(arr[k], p);
		}
	}
	for(int i = 1; i <= m; i++) {
		total += arr[i];
	}
	cout<<total;
}