var
a:array[1..1000] of longint;
i,j,n,t,t1,t2,m:longint;
begin
readln(t,m);
fillchar(a,sizeof(j),0);
for i:=1 to m do
begin
readln(t1,t2);
for j:=t-t1 downto 0 do if a[j]+t2>a[j+t1] then a[j+t1]:=a[j]+t2;
end;
writeln(a[t]);
end.

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>


using namespace std;

int main(){
    int t, m;
    cin >> t >> m;
    int time[m + 1];
    int value[m + 1];
    for (int i = 1; i <= m; i++){
        cin >> time[i] >> value[i];
    }
    
    int dp[m + 1][t + 1];
    memset(dp, 0, sizeof(dp));
    for (int i = 1; i <= m; i++){
        for (int j = 0; j <= t; j++){
            if (j - time[i] >= 0) dp[i][j] = max(dp[i - 1][j], dp[i - 1][j - time[i]] + value[i]);
            else dp[i][j] = dp[i - 1][j];
        }
    }
    
    cout << dp[m][t] << endl;
    return 0;
}