#include<bits/stdc++.h> #define int long long using namespace std; int a[26900],o,ans; signed main(){ for(int i=1;i<=7000;i++){ int y=i,b[5],p=0,s; if(i>0&&i<10)s=1; if(i>=10&&i<100)s=2; if(i>=100&&i<1000)s=3; if(i>=1000&&i<=7000)s=4; while(y!=0){ b[++p]=y%10; y/=10; } for(int i=s;i>=1;i--){ a[++o]=b[i]; } } for(int i=1;i<=26893-3;i++){ if(a[i]==2&&a[i+1]==0&&a[i+2]==2&&a[i+3]==6){ cout<<i<<" "<<i+1<<" "<<i+2<<" "<<i+3<<"\n"; ans++; } } cout<<ans; return 0; } #include<bits/stdc++.h> #define int long long using namespace std; int s=0; signed main(){ for(int i=1;i<=2620;i++){ if(i>0&&i<10)s++; if(i>=10&&i<100)s+=2; if(i>=100&&i<1000)s+=3; if(i>=1000&&i<=7000)s+=4; } //2620 //9372 cout<<s; return 0; } 袋鼠数学竞赛C级第30题答案。