import macros;macro ImportExpand(s:untyped):untyped = parseStmt($s[2])
{.checks: off.}
import sequtils
proc scanf(formatstr: cstring){.header: "<stdio.h>", varargs.}
proc ii(): int {.inline.} = scanf("%lld\n", addr result)

var n, p, k = ii()
var tb = newSeqWith(n, (ii(), ii()))
var dp = newSeqWith(k+1, -1)
dp[0] = p
const mx = 1000_000_000_000_000_000
for (t, b) in tb:
    var dpn = dp
    for i in 0..<k:
        if dp[i] == -1: continue
        if t == 1: dpn[i+1] = max(dpn[i+1], dp[i] + b)
        else: dpn[i+1] = max(dpn[i+1], dp[i] * 2)
    swap(dp, dpn)
    # must be WA
    if dp[^1] >= mx:
        echo -1
        quit()
echo dp[^1]