View Compilation Error

0_0_18686697_20172.cpp:17:8: error: 'N' was not declared in this scope
 char s[N], t[70];
        ^
0_0_18686697_20172.cpp: In function 'int main()':
0_0_18686697_20172.cpp:20:10: error: 's' was not declared in this scope
     gets(s+1);
          ^