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;
}

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() {
double x,y;
char c1,c2,c3;
int a1,a2,a3;
 scanf("%d%d%d",&a1,&a2,&a3);
 printf("%d,%d,%d\n",a1,a2,a3);
 scanf("%c%c%c",&c1,&c2,&c3);
 printf("%c%c%c\n",c1,c2,c3);
 scanf("%f,%lf",&x,&y);
 printf("%lf,%lf\n",x,y);

 return 0;
}

#include <stdio.h>
 int main() {
 char ans1, ans2;
 printf("复习了没?");
 ans1 = getchar();
 getchar();
 printf("\n动手敲代码了没? ");
 ans2 = getchar();
 if(ans1=='Y'&&ans2=='Y'||ans1=='y'&&ans2=='Y'||ans1=='y'&&ans2=='y'||ans1=='Y'&&ans2=='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<'9'&&x>'0')
printf("%c是数字字符\n", x);
else if( 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>
#include<math.h>
int main()
{
int n;
double sum,q,i;
q=2.0;
sum=1;
scanf("%d",&n);
for(i=1;i<=n;i++)
sum=sum+pow(q,i);
printf("n=%d时，sum=%.0f",n,sum);
return 0;
}