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