Force buckle ------ replace blank space

char* replaceSpace(char* s){
    
    int len =strlen(s);
    char* s1=(char*)calloc(2000,sizeof(char));
    int count=0;
    for(int a=0;a<len;a++){
    
        if(s[a]!=' '){
    
            s1[count++]=s[a];
        }
        else{
    
            s1[count++]='%';
            s1[count++]='2';
            s1[count++]='0';
        }
    }
    s1[count]='\0';
    return s1;
}