R=range
J=lambda:map(int,input().split())
N,P,K=J()
D=[P]+[0]*K
for i in R(N):
	T,B=J()
	for k in R(K,0,-1):D[k]=max(D[k],D[k-1]+[B,D[k-1]][T-1])
print([D[K],-1][D[K]>10**18])