#include<cstring>

using namespace std;

int main()

{

int utime[101],vau[101],imp[101];

int num,time,tot,temp,unum=0;

cin>>time>>num;

for(int i=1;i<=num;++i)

{

cin>>utime[i]>>vau[i];

imp[i]=vau[i]/utime[i];

}

for (int i=1;i<num;++i)

for (int j=1;j<num;++j)

{

if(imp[j]<imp[j+1])

{

temp=imp[j];imp[j]=imp[j+1];imp[j+1]=temp;

temp=vau[j];vau[j]=vau[j+1];vau[j+1]=temp;

temp=utime[j];utime[j]=utime[j+1];utime[j+1]=temp;

}

}

int i=1;

int js=1;

while(time>=0&&(i<=num&&js<=num))

{

if(time>=utime[i])

{

unum+=vau[i];

time-=utime[i];

}

i++;

js++;

}

cout<<unum;

}