```go
package main

import (
	"fmt"
	"io"
	"os"
)

func main() {
	input, err := io.ReadAll(os.Stdin)
	if err != nil && err != io.EOF {
		// Proceed with whatever was read
	}
	pos := 0

	skipWhitespace := func() {
		for pos < len(input) && input[pos] <= ' ' {
			pos++
		}
	}

	skipWhitespace()
	if pos >= len(input) {
		return
	}
	start := pos
	for pos < len(input) && input[pos] > ' ' {
		pos++
	}
	original := input[start:pos]

	skipWhitespace()
	k := 0
	for pos < len(input) && input[pos] > ' ' {
		k = k*10 + int(input[pos]-'0')
		pos++
	}

	skipWhitespace()
	n := 0
	for pos < len(input) && input[pos] > ' ' {
		n = n*10 + int(input[pos]-'0')
		pos++
	}

	s := make([]byte, 0, k)
	if len(original) > k {
		s = append(s, original[:k]...)
	} else {
		s = append(s, original...)
	}

	mangledBuf := make([]byte, k)

	for i := 0; i < n; i++ {
		skipWhitespace()
		if pos >= len(input) {
			break
		}
		l := 0
		for pos < len(input) && input[pos] > ' ' {
			l = l*10 + int(input[pos]-'0')
			pos++
		}
		skipWhitespace()
		r := 0
		for pos < len(input) && input[pos] > ' ' {
			r = r*10 + int(input[pos]-'0')
			pos++
		}

		l-- 
		r-- 

		if r >= k {
			continue
		}

		L := r - l + 1
		oldLen := len(s)
		newLen := oldLen + L
		if newLen > k {
			newLen = k
		}

		needed := newLen - (r + 1)
		if needed > L {
			needed = L
		}
		if needed <= 0 {
			continue
		}

		evenStart := l + 1
		evenEnd := r
		evenCount := 0
		if evenStart <= evenEnd {
			evenCount = (evenEnd - evenStart)/2 + 1
		}

		takeEven := evenCount
		if takeEven > needed {
			takeEven = needed
		}

		if takeEven > 0 {
			_ = mangledBuf[takeEven-1]
			_ = s[evenStart+(takeEven-1)*2]
			for j := 0; j < takeEven; j++ {
				mangledBuf[j] = s[evenStart+j*2]
			}
		}

		idx := takeEven
		if idx < needed {
			takeOdd := needed - idx
			oddStart := l
			if takeOdd > 0 {
				_ = mangledBuf[idx+takeOdd-1]
				_ = s[oddStart+(takeOdd-1)*2]
				for j := 0; j < takeOdd; j++ {
					mangledBuf[idx+j] = s[oddStart+j*2]
				}
			}
		}

		s = s[:newLen]

		if r+1+L < newLen {
			copy(s[r+1+L:newLen], s[r+1:oldLen])
		}

		copy(s[r+1:newLen], mangledBuf[:needed])
	}

	fmt.Println(string(s))
}
```