#include <iostream>
#include <fstream>
#include <climits>
using namespace std;

int main()
{
    ifstream f("buline.in");
    ofstream g("buline.out");
    long long int i,j,n,N,x,y,v[1000],z,s=0,max=INT_MIN,MAX=INT_MIN;
    f>>N;
    for(i=1;i<=N;i++){
        f>>x>>y;
        if(y==0)v[i]=v[i+N]=-x;
            else v[i]=v[i+N]=x;
    }
for(i=1;i<=N;i++){
    for(j=1;j<=N;j++){
        for(z=1;z<=j;z++){
            s=s+v[z];}
    if(s>max)max=s;
}
 if(max>MAX)MAX=max;
}
    g<<MAX;












}