#include<stdio.h>
#include<stdli.b>
struct node
{
    int data;
    struct node*next;
}*head=NULL,*tail;
int main()
{
    int o,v,flag=o;
    scanf("%d",%d,&o,&v)
    struct node*temp=head;
    while(temp)
    {
        if(temp->data==o)
    {
        temp->data=v
        flag=i
        {
            temp=temp->next;
        }
        if(flag==o)
        printf("Invaild not found");
        else
        while(head)
        {
            printf("%d",head->data);
            head=head->next;
        }
    }
        }
        }
    }
}