#include <stdio.h>
int main() {
int num;
scanf("%d", &num);
printf("2049%04d\n", num);
scanf("%d", &num);
printf("2049%04d\n", num);
scanf("%d", &num);
printf("2049%04d\n", num);
return 0;
}

#include <stdio.h>
int main() {
int x=1234;
float f=123.456;
double m=123.456;
char ch='a';
char a[]="Hello, world!";
int y=3, z=4;
printf("%d %d\n", y, z);
printf("y=%d, z=%d\n", y,z);
printf("%8d,%2d\n", x,x);
printf("%f, %8f, %8.1f, %0.2f, %.2e\n",f,f,f,f,f);
printf("%lf\n",m);
printf("%3c\n", ch);
printf("%s\n%15s\n%10.5s\n%2.5s\n%.3s\n",a,a,a,a,a);
return 0;
}

#include <stdio.h>
int main() {
char ans1, ans2;
printf("复习了没? (输入y或Y表示复习了，输入n或N表示没复习) : ");
ans1 = getchar(); // 从键盘输入一个字符，赋值给ans1
getchar(); 
printf("\n动手敲代码了没? (输入y或Y表示敲了，输入n或N表示木有敲) : ");
ans2 = getchar();
if(ans1=='y'||'Y'&&ans2=='y'||'Y')
printf("\n罗马不是一天建成的:)\n");
else
printf("\n罗马不是一天毁灭的。。。\n");
return 0;
}

#include <stdio.h>
int main() {
char x;
x = getchar();
if(x>='0'&&x<='9' ) 
printf("%c是数字字符\n", x);
else if(x>='A'&&x<='Z'||x>='a'&&x<='z') 
printf("%c是英文字母\n", x);
else
printf("%c是其它字符\n", x);
return 0;
}

#include<stdio.h> 
int main()
{
    int i=0,c,m=1;
    scanf("%d",&c);
    
    
    do
    {m=m*2;
    i=i+1;
    
    }while(i!=c);
m=m-1;
        
    printf("n=%d时,sum=%d",c,m);
    return 0;
}