Language: C

char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}

Compiler output:
main.c:1:16: warning: data definition has no type or storage class
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
      |                ^
main.c:1:16: error: type defaults to 'int' in declaration of 'k' [-Wimplicit-int]
main.c:1:18: error: type defaults to 'int' in declaration of 'u' [-Wimplicit-int]
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
      |                  ^
main.c:1:20: error: type defaults to 'int' in declaration of 'p' [-Wimplicit-int]
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
      |                    ^
main.c:1:22: error: type defaults to 'int' in declaration of 'c' [-Wimplicit-int]
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
      |                      ^
main.c:1:24: error: return type defaults to 'int' [-Wimplicit-int]
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
      |                        ^~~~
main.c: In function 'main':
main.c:1:35: error: implicit declaration of function 'gets' [-Wimplicit-function-declaration]
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
      |                                   ^~~~
main.c:1:122: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
      |                                                                                                                          ^~~~~~
main.c:1:1: note: include '<stdio.h>' or provide a declaration of 'printf'
  +++ |+#include <stdio.h>
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
main.c:1:122: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
      |                                                                                                                          ^~~~~~
main.c:1:122: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:1:145: error: implicit declaration of function 'exit' [-Wimplicit-function-declaration]
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
      |                                                                                                                                                 ^~~~
main.c:1:1: note: include '<stdlib.h>' or provide a declaration of 'exit'
  +++ |+#include <stdlib.h>
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
main.c:1:145: warning: incompatible implicit declaration of built-in function 'exit' [-Wbuiltin-declaration-mismatch]
    1 | char s[999],*v;k,u,p,c;main(){for(gets(s),v=s;*v;v++)*v-'K'||k++,*v-'U'||u++,*v-'P'||p++,*v-'C'||c++;k=u<k?u:k;k=p<k?p:k;printf("%d\n",c<k?c:k);exit(0);}
      |                                                                                                                                                 ^~~~
main.c:1:145: note: include '<stdlib.h>' or provide a declaration of 'exit'