##JavaScript (ES6), 71 bytes

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    f=([a,...b])=>a?(+a&(a+=b[0])+b[1]<123|a>47&a<58|a>64&a<91|a>96)+f(b):0

###Test cases

<!-- begin snippet: js hide: true console: true babel: false -->

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    f=([a,...b])=>a?(+a&(a+=b[0])+b[1]<123|a>47&a<58|a>64&a<91|a>96)+f(b):0

    console.log(f("5698"))                // 3
    console.log(f("564693"))              // 2
    console.log(f("530923864209124521"))  // 3
    console.log(f("1111111"))             // 5
    console.log(f("5115643141276343"))    // 4
    console.log(f("56789"))               // 4
    console.log(f("94"))                  // 0
    console.log(f("1"))                   // 0


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