Count substrings contains only given character

Given a string S and a character C, write a program to count the number of substrings of S that contains only the character C.

Sample Input
0110111
1
Sample Output
9

#include<stdio.h>
int main() {
  char str[30];
  int i,ch,c=0,SubstrCount=0;
  fgets(str,30,stdin);
  scanf("%c",&ch);
  for(i=0;str[i]!='\0';i++){
    if(str[i]==ch){
      c++;
    }else{
      SubstrCount += (c*(c+1))/2;
      c=0;
    }
  }
  SubstrCount += (c*(c+1))/2;
  printf("%d",SubstrCount);
  return 0;
}