#include <iostream>
using namespace std;
int
sigmat, n, t[101], value[101], ans[1001];
void
__read__()
{
cin >> sigmat >> n;
for( int i = 1; i <= n; i++ )
cin >> t[i] >> value[i];
}
void
__dp__()
{
for( int i = 1; i <= n; i++ )
for( int j = sigmat; j >= t[i]; j-- )
if( ans[j] < ans[j - t[i]] + value[i] )
ans[j] = ans[j - t[i]] + value[i];
}
void
__outp__()
{
int max = 0;
for( int i = sigmat; i > 0; i-- )
if( max < ans[i] )
max = ans[i];
cout << max << endl;
}
int
main()
{
__read__();
__dp__();
__outp__();
return 0;
}