#include<bits/stdc++.h>
using namespace std;
int m,n,zl,jg,sum;
int minn[100086];
int main( ){
    cin>>m>>n;
    for (int i=1;i<=m;i++)
        minn[i]=INT_MAX;
    for (int i=1;i<=n;i++)
        cin>>zl>>jg,minn[zl]=min(minn[zl],jg);
    for (int zl=1;zl<=m;zl++)
        sum+=minn[zl];
    cout<<sum;
    return 0;
}