N,P,K=map(int,input().split())
T=[]
B=[]
for _ in range(N):
    t,b=map(int,input().split())
    T.append(t)
    B.append(b)

INF=int(1e18)
dp=[[0 for _ in range(K+1)] for _ in range(N+1)]
dp[0][0]=P

for i in range(1,N+1):
    for j in range(0,K+1):
        if dp[i-1][j]==0:continue
        dp[i][j]=max(dp[i][j],dp[i-1][j])
        if T[i-1]==1 and j<K:
            dp[i][j+1]=max(dp[i][j+1],dp[i-1][j]+B[i-1])
        if T[i-1]==2 and j<K:
            dp[i][j+1]=max(dp[i][j+1],dp[i-1][j]*2)
ans=dp[N][K]
if ans>INF:print(-1)
else:print(ans)