n=int(input())
s=input().split("0")
ans=1

p=0
m=0
vp=[]
vm=[]
for i,si in enumerate(s):
    if len(si)==0:
        ans=max(ans,m+1)
    else:
        np=0
        nm=0
        f=[0]
        for sii in si:
            if sii=="-":
                nm+=1
                f.append(f[-1]+1)
            else:
                np+=1
                f.append(f[-1])
        vp.append(np)
        vm.append(nm)
        f=f[1:]
        si=si[::-1]
        b=[0]
        for sii in si:
            if sii=="+":
                b.append(b[-1]+1)
            else:
                b.append(b[-1])
        b=b[1:]
        b.reverse()
        for fi,bi in zip(f,b):
            ans=max(ans,fi+bi+1)

        if i==0:
            ans=max(ans,nm)
            ans=max(ans,np)
        else:
            ans=max(ans,m+np+1)
        m=nm
        p=np


for i in range(len(vp)):
    for j in range(i+1,len(vp)):
        ans=max(ans,vm[i]+vp[j]+1)
    
print(ans)