#include<stdio.h>
#include<stdlib.h>
int g,w,eg[30],cg[30],i,c;
int main()
{
    FILE*f=fopen("energii.in","r"); FILE*h=fopen("energii.out","w");
    fscanf(f,"%d%d",&g,&w);
    fscanf(f,"%d%d",&eg[0],&cg[0]);
    c=cg[0];
    for(i=1;i<g;i++)
    {
        fscanf(f,"%d%d",&eg[i],&cg[i]);
        if(cg[i]>c) c=cg[i];

    }
    fprintf(h,"%d",c);
    fclose(f); fclose(h);
    return 0;
}