#include<algorithm>
using namespace std;

#define DIM 200001
#define INF -1000001

int n,a[2*DIM];

void solve(){
    int i,j,cul,max0;

    scanf("%d",&n);
    for(i=1; i<=n; ++i){
        scanf("%d%d",&a[i],&cul);
        if(!cul)
            a[i]*=-1;}
    for(i=1; i<=n; a[i+n]=a[i],++i);
    for(i=1; i<=2*n; a[i]+=a[i-1],++i);
    for(i=1,max0=INF; i<=2*n; ++i)
        for(j=i+1; j<=i+n&&j<=2*n; ++j)
            if(a[j]-a[i]>max0)
                max0=a[j]-a[i];
    printf("%d",max0);
    /*for(i=1; i<=2*n; ++i)
        printf("%d ",a[i]);*/}

int main(){

    freopen("buline.in","r",stdin);
    freopen("buline.out","w",stdout);
    solve();
    return 0;}