#include<cstdio>
#include<cctype>
#include<algorithm>
using namespace std;
inline int read(){
    char c; while(c=getchar(),!isdigit(c)); int x=c-‘0‘;
    while(c=getchar(),isdigit(c)) x=x*10+c-‘0‘; return x;
}
int f[1001];
int main(){
    int t=read(),m=read();
    while(m--){
        int v=read(),x=read();
        for(int i=t;i>=v;i-=1)
            f[i]=max(f[i-v]+x,f[i]);
    }
    printf("%d",f[t]);
    return 0;
}