#include<bits/stdc++.h>
using namespace std;
#define ll long long
ll n,m,a[22],b[22],dp[22][220],tmp;
int main(){
	freopen("topic.in","r",stdin);
	freopen("topic.out","w",stdout);
	cin>>n>>m;
	for(int i=1;i<=m;i++)cin>>a[i]>>b[i];
	memset(dp,120,sizeof dp);
	dp[0][0]=0;
	for(int i=1;i<=m;i++){
		dp[i][0]=0;
		for(int j=1;j<=n;j++){
			for(int k=0;k<=j;k++){
				tmp=a[i]*pow((double)k,(double)b[i]);
				dp[i][j]=min(dp[i][j],dp[i-1][j-k]+tmp);
			}
		}
	}
	cout<<dp[m][n];
	return 0;
}