#janken
G,C,P=(int(i) for i in input().split())
S=input()
#rint (G)
T=0
for i in range(len(S)):
#    print (i)
    if S[i]=="G" and P>0:
        T+=1
        P-=1
    if S[i]=="C" and G>0:
        T+=1
        G-=1
    if S[i]=="P" and C>0:
        T+=1
        C-=1
print(T)