string contains operator or not

#include<stdio.h>

#include<string.h>

int main()

{

char str[100];

int i;

int op=0;

printf("Enter a string: ");

fgets(str,sizeof(str),stdin);

int length=strlen(str);

for(i=0;i<=length;i++)

{

if(str[i]=='+'||str[i]=='-'||str[i]=='*'||str[i]=='/'||str[i]=='%'||str[i]=='>'||str[i]=='<')

{

op++;

}

}

if(op>0)

{

printf("The string contains an operator");

}

else

{

printf("The string does not contain any  operator");

}

}