#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define MAXN 210
inline ll read(){
	ll x=0,f=1;
	char c=getchar();
	while(c<'0'||c>'9'){
		if(c=='-')f=-1;
		c=getchar();
	}
	while(c>='0'&&c<='9'){
		x=x*10+c-'0';
		c=getchar();
	}
	return x*f;
}
ll n,m;
ll dp[MAXN][MAXN];
ll ksm(ll ds,ll zs){
	ll ans=1,now=ds;
	while(zs){
		if(zs&1)ans*=now;
		now*=now;
		zs/=2;
	}
	return ans;
}
int main(){
	freopen("topic.in","r",stdin);
	freopen("topic.out","w",stdout);
	n=read(),m=read();
	memset(dp,126,sizeof(dp));
	dp[0][0]=0;
	for(int i=1;i<=m;i++){
		dp[i][0]=0;
		ll a=read(),b=read();
		for(int j=1;j<=n;j++){
			for(int u=0;u<=j;u++){
				dp[i][j]=min(dp[i][j],dp[i-1][j-u]+a*ksm(u,b));
			}
		}
	}
	cout<<dp[m][n];
	return 0;
}