#include<iostream>
#include<cmath>
#include<cstdio>
using namespace std;
long long f[21][300],n,m,a[210],b[210],ans;
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];
	}
	for(int i=1;i<=m;i++){
		for(int j=1;j<=n;j++){
			for(int k=0;k<=j;k++){
				long long p=a[i]*pow(k,b[i]);
				if(f[i][j]==0||i==1){
					f[i][j]=f[i-1][j-k]+p;			
				}
				else{
					f[i][j]=min(f[i-1][j-k]+p,f[i][j]);	
				}
			}
		}
	}
	cout<<f[m][n];
	fclose(stdin);
	fclose(stdout);
	return 0;
}