由于符合要求的数还是相当密集的，所以本题可以采取暴力，如果范围扩到1e18则可以数位dp
1 #define mm(a) memset(a,0,sizeof(a)); 2 #define max(x,y) (x)>(y)?(x):(y) 3 #define min(x,y) (x)<(y)?(x):(y) 4 #define Fopen freopen("1.in","r",stdin); freopen("m.out","w",stdout); 5 #define rep(i,a,b) for(ll i=(a);i<=(b);i++) 6 #define per(i,b,a) for(ll i=(b);i>=(a);i--) 7 #include<bits/stdc++.h> 8 typedef long long ll; 9 #define PII pair<ll,ll> 10 using namespace std; 11 const int INF=0x3f3f3f3f; 12 const int MAXN=(int)2e6+5; 13 14 int n; 15 16 bool ck(int x) { 17 if(x%7==0)return 0; 18 while(x) { 19 if(x%10==7)return 0; 20 x/=10; 21 } 22 return 1; 23 } 24 int main() { 25 while(~scanf("%d",&n)) { 26 int x=0; 27 while(n) { 28 x++; 29 if(ck(x))n--; 30 } 31 printf("%d ",x); 32 } 33 return 0; 34 }