#include <stdio.h>
#include <algorithm>
#include <memory.h>
using namespace std;
int result[1001][101];
int w[101],v[101];
int main()
{
int totalTime , count;
memset(result , 0 ,sizeof(result));
scanf("%d %d" , &totalTime , &count);
for ( int i = 1 ;i <= count ; i++)
scanf("%d %d" , &w[i] , &v[i]);
for ( int i = 1 ; i <= totalTime ; i++)
for (int j = 1 ; j <= count ; j++)
{
if ( i - w[j] >= 0 )
result[i][j] = max(result[i][j-1] , result[ i - w[j]][j-1]+v[j]) ;
else
result[i][j] = result[ i ][ j -1];
}
printf("%d\n" ,result[totalTime][count]);
return 0 ;
}