Changes 'a' & 'b' to '-' in file using file handling

#include<stdio.h>

int main()
{
FILE *p1, *p2;
char f1[20], f2[20];
char ch;

printf("Enter File name which has to be copied: ");
gets(f1);
p1=fopen(f1,"r");

if(p1==NULL)
{
    printf("\nUnable to open %s",f1);
    return 1;
}

printf("Enter Destination file");
gets(f2);
p2=fopen(f2,"w");

if(p2==NULL)
{
    printf("Cannot open %s",f2);
    return 1;
}

while((ch=fgetc(p1))!=EOF)
{
    if(' ' || 'a' || 'b')
        ch='-';
    fputc(ch,p2);
}
printf("Completed");
fclose(p1);
fclose(p2);
return 0;
}