1 #include <stdio.h> 2 #include <string.h> 3  4 #define MAXLEN 71 5  6 int length; 7  8 void toCode(int code[],char text[]){ 9     int i;10     for(i=0;i<length;i++){11         if(text[i] == ‘_‘)12             code[i] = 0;13         else if(text[i] == ‘.‘)14                 code[i] = 27;15             else16                 code[i] = text[i] - 96;17     }18 }19 20 void toText(char text[],int code[]){21     int i;22     for(i=0;i<length;i++){23         if(code[i] == 0)24             text[i] = ‘_‘;25         else if(code[i] == 27)26                 text[i] = ‘.‘;27             else28                 text[i] = code[i] + 96;29     }30     text[i] = 0;31 }32 33 int inRange(int n){34     if(n>=0&&n<=27)35         return 1;36     return 0;37 }38 39 void untwist(char textC[],int k){40     int i,j;41     int codeC[MAXLEN],codeP[MAXLEN];42     char textP[MAXLEN];43 44     toCode(codeC,textC);45     for(i=0;i<length;i++){46         j = (k*i)%length;47         if(inRange(codeC[i] + i)) 48             codeP[j] = codeC[i] + i;49         else if(inRange(codeC[i] + i - 28)) 50                 codeP[j] = codeC[i] + i - 28;51             else if(inRange(codeC[i] + i - 56)) 52                     codeP[j] = codeC[i] + i - 56;53                 else if(inRange(codeC[i] + i - 84)) 54                         codeP[j] = codeC[i] + i - 84;55     }56     toText(textP,codeP);57     printf("%s\n",textP);58 }59 60 int main(){61     int k;62     char textC[MAXLEN];63     while(scanf("%d",&k)&&k){64         scanf("%s",textC);65         length = strlen(textC);66         untwist(textC,k);67     }68     return 0;69 }